President Barack Obama cautioned Tuesday against rushing headlong to take action against Syria’s ruling regime, cautioning that his administration must gather more evidence before involving itself in that country’s civil war.

The president said that while evidence suggested that chemical weapons were used in Syria – thereby crossing the “red line” Obama had established in the Syrian conflict – more details were needed, namely about who used those weapons, and when.

Pablo Martinez Monsivais / AP

President Barack Obama arrives to answers questions during his new conference in the Brady Press Briefing Room of the White House on Tuesday, April 30, 2013.

“When I am making decisions about America’s national security and the potential for taking additional action in response to chemical weapons use, I’ve got to make sure I’ve got the facts,” Obama said at his first press conference in two months.

"And if we end up rushing to judgment without hard, effective evidence, then we can find ourselves in a position where we can't mobilize the international community to support what we do."

The situation in Syria and other issues of national security – a hunger strike at the terrorist detention facility at Guantanamo Bay, Cuba, and the government's response to the terrorist attack at the Boston Marathon earlier this month – have dominated much of the president's agenda over the past month. 

The hunger strike – the military said on Monday that 100 of 166 detainees had participated in the strike protesting conditions at Guantanamo Bay – prompted the president to renew his call for closing the prison. While the president signed an order early in his first term to shutter the facility, lawmakers in both parties have stymied Obama's efforts to achieve that goal. 

"I continue to believe that we’ve got to close Guantanamo. I think it is critical for us to understand that Guantanamo is not necessary to keep America safe," Obama said. "It is expensive, it is inefficient, it hurts us in terms of our international standing, it lessens cooperation in terms of our allies in counterterrorism efforts, it is a recruitment tool for extremists. It needs to be closed."

Moreover, the president pledged to "go back at" the issue, adding that his administration was reviewing ways to achieve its goal of closing the prison, perhaps by returning to Congress for permission. 

The theme of international cooperation, though, recurred throughout Obama's remarks about these tricky foreign policy issues.

The president, for instance, stressed the need for the United States to act in concert with international allies in response to the situation in Syria, and said the U.S. and its partners were already “deeply invested” in trying to find a solution to the situation in Syria.

But Obama was reluctant to specify what actions his administration might take. “By ‘game-changer’ I mean that we would have to rethink the range of options that are available to us,” he said.

A bipartisan group of lawmakers has expressed reluctance to making a U.S. military incursion into Syria, though more hawkish Republicans have called for targeted strikes to help cripple parts of the Syrian military and assist rebels against the Assad regime.

Obama also said he'd worked with Russian President Vladimir Putin on the situation in Syria, but also the intelligence response to the April 15 bombings at the Boston Marathon.

Amid questions about whether the government failed to heed Russian intelligence warnings about the radicalization of the suspects in the bombing, Director of National Intelligence James Clapper ordered a review on Tuesday into the U.S. government's handling of intelligence in the case. 

"When an event like this happens, we want to go back and review every step that was taken," the president explained. "We want to leave no stone unturned. We want to see if, in fact, there's additional protocols and procedures that could be put in place that would further improve and enhance our ability to detect a potential attack."

Slideshow: Syria uprising

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A look back at the conflict that has overtaken the country.

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This story was originally published on Tue Apr 30, 2013 10:54 AM EDT

A bipartisan slate of political leaders pondered what role the United States should play in Syria following indications that its besieged leader used chemical weapons in that country's civil war. 

Following the Obama administration's declaration this week that Syrian leader Bashar al-Assad had used chemical weapons against rebels looking to unseat him, lawmakers pondered how to best respond. President Barack Obama had previously called the use of such weapons a "red line" that would prompt a response from the United States.

Sen. John McCain, R-Ariz., a senior member of the Senate Armed Services Committee, urged the president to begin identifying a strategy to secure Syria's stockpiles of chemical weapons should the government fall.

"Be prepared with an international force to go in and secure these stocks of chemical, and perhaps biological, weapons," McCain said on NBC's "Meet the Press."

But, mindful of Americans' war-weariness following nearly a decade of war in Iraq and Afghanistan, McCain cautioned against sending U.S. troops to Syria, warning that it could prompt resentment from Syrians. 

The Arizona senator said in the meanwhile that Obama could establish a no-fly zone in Syria without endangering any U.S. troops. And McCain also called for Obama to further arm rebel groups. 

The White House has been more cautious, explaining this week in briefings to lawmakers that evidence of the use of chemical weapons in Syria is still preliminary, and the government would take more time to gather intelligence. 

"To use potential weapons of mass destruction on civilian populations crosses another line with respect to international norms and international law.  And that is going to be a game changer," Obama said Friday before meeting with King Abdullah II of Jordan.

"We have to act prudently. We have to make these assessments deliberately," the president added. "But I think all of us, not just in the United States but around the world, recognize how we cannot stand by and permit the systematic use of weapons like chemical weapons on civilian populations."

The administration's caution reflects the difficulty in navigating the situation in Syria. A key concern involves identifying which rebels to arm in Syria, and whether there is a risk of those arms being turned back agains the U.S. in the future. 

"My concern is that al Qaeda has more influence among the rebels than it should," said Rep. Peter King, R-N.Y., a key lawmaker who serves on intelligence and homeland security panels. 

But even beyond the national security implications, some lawmakers have said there might be humanitarian justifications to act in Syria.

"I think the United States could play a bigger role in dealing with the humanitarian crisis," said Rep. Keith Ellison, D-Minn., one of two Muslim members of Congress. "I don't think the world's greatest super power, the United States, can stand by and do nothing."

This story was originally published on Sun Apr 28, 2013 9:33 AM EDT

Updated at 8:40a.m.ET: PORT ST. LUCIE, Fla. – In a major foreign policy speech Monday Mitt Romney will attempt to stake out a more activist public position than President Barack Obama on supporting the rebels in Syria's civil war. Romney plans to say that he believes in working with partner nations to arm rebels fighting the government of Syrian President Bashir al-Assad.

Slideshow: Behind Syrian rebel lines

Machine guns operated by motorcycle brakes? Get a glimpse at the rebels fighting against Assad's forces in Syria's mountainous Jabal al-Zawiya area.

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He would equip the rebels – “who share our values” -- with heavy weapons to take out "tanks, helicopters and fighter jets," according to the remarks. The Obama administration has refrained from doing so out of concern that the weapons would end up in terrorist hands, according to The New York Times.

Romney will also argue that the U.S. must support the rebels to develop influence and good relations with the Syria’s future leaders.

Slideshow: On the campaign trail

Reuters, Getty Images

In the final push in the 2012 presidential election, candidates Mitt Romney and Barack Obama make their last appeals to voters.

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Syria is just one area Romney will touch on in a speech in which the Republican nominee will attempt to portray himself as a leader firmly in the peace-through-strength tradition of Harry Truman and Ronald Reagan, while casting President Obama as an ineffective leader on a dangerous and constantly-evolving world stage.

Related: Who are the Syrian rebels?

Romney will deliver a 30-minute address, titled "The Mantle of Leadership," later Monday at the Virginia Military Institute, his 10th address on the topic of foreign policy since summer 2011.

Recommended: Obama urges supporters not to lose enthusiasm

The former Massachusetts governor's speech, like the others before it, will focus on a vision of peace through strength. It will include new details on how Romney would address current global hotspots and repeat regular stump speech staples – such as the importance of averting planned defense cuts, expanding and reinvesting in the U.S. military and working closely with allies abroad, especially Israel.

In prepared remarks released Sunday to reporters, Romney laid out global issues where his campaign hopes to draw "great contrast" with Obama – notably on Libya, Syria and Egypt.

Slideshow: Mitt Romney's life in politics

Jonathan Ernst / Getty Images

From governor's son to presidential contender, a look at the life of Republican Mitt Romney.

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The speech links the attack on the American consulate in Benghazi last month to al-Qaida, a position Romney has rarely engaged in on the campaign trail. Romney calls the attack "likely the work of the same forces that attacked our homeland on September 11th, 2001," and "the deliberate work of terrorists." The attack was not, he says, a spontaneous response to a movie trailer maligning the Muslim Prophet Mohammad, as the Obama administration initially said.

As he did at the Clinton Global Initiative last month, Romney will argue that U.S. aid to Egypt should be linked with promises from Egyptian leaders to uphold the 1979 peace treaty with Israel and to protect minorities, including the country’s Coptic Christians.

Romney, who offended some Palestinians with remarks he made in Israel suggesting the economic disparities between the Palestinian territories and Israel were based in part on cultural differences, will also promise to "recommit" to helping form a democratic Palestinian state alongside Israel.

"In this old conflict, as in every challenge we face in the Middle East, only a new President will bring the chance to begin anew," say Romney’s prepared remarks.

On the infamous "47 percent" tape of a Florida fundraising event in May, Romney predicted the Israeli/Palestinian conflict would "remain [an] unsolved problem."

"We have a potentially volatile situation, but we sort of live with it," Romney said at the May fundraiser, comparing the peace process to the decades-long standoff between China and Taiwan. "And we kick the ball down the field and hope that ultimately somehow, something will happen to resolve it."

During a Sunday conference call with reporters, Romney foreign policy advisers said Monday’s foreign policy speech was meant to align Romney with the foreign policy tradition of Harry Truman, Ronald Reagan and George Marshall.

"If you look at Harry Truman and John Kennedy and the use of power by Bill Clinton in his second term that is a much different approach than Jimmy Carter and Barack Obama so I do think it’s a bipartisan tradition, it’s a recognition that strength is not provocative, its weakness that’s provocative," former Ambassador Rich Williamson, a Romney foreign policy adviser, said on the call. "There’s a fundamental difference between Barack Obama and Mitt Romney and that’s part of the choice that American voters will be asked to make."

Democrats fired back preemptively at that characterization.

"Mainstream foreign policy isn't what Mitt Romney is putting forward: having plans to start wars but not end them; wanting to keep 30,000 U.S. troops in Iraq indefinitely; exploding our defense spending to levels the Pentagon has not asked for, with no way to pay for it; insulting our allies and partners around the world on the campaign trail; and calling Russia our number-one geopolitical foe," Obama campaign spokesperson Lis Smith said in a statement Sunday. "If that's where Mitt Romney thinks the mainstream is, he needs to find a better compass."

Aboard Air Force One Sunday, Jen Psaki, the Obama campaign's traveling press secretary, was more cutting when asked her views on the speech.

"We're not going to be lectured by someone who has been an unmitigated disaster on foreign policy every time he's dipped his toe in the foreign policy waters," Psaki told reporters. "The only person who has offended Europe more is probably Chevy Chase."

President Barack Obama said he would have to rethink his current opposition to U.S. military engagement in Syria if the regime there were to use or move its chemical and biological weapons.

The president told NBC's Chuck Todd that he couldn't be "absolutely confident" that the stockpiles of weapons possessed by Bashar al-Assad's regime were completely secure.

"What I'm saying is we're monitoring that situation very carefully," Obama said in a surprise appearance in the White House briefing room.

But if the Assad regime were to use its weapons stockpiles, or alternatively, move it around, Obama suggested military action could be on the table.

"We have been very clear to the Assad regime, but also to other players on the ground, that a red line for us is we start seeing a whole bunch of chemical weapons moving around or being utilized," the president said. "That would change my calculus. That would change my equation."

Earlier this month, when asked about contingency planning for the Syrian conflict, Secretary Hillary Clinton drew the "red line" at only the use of chemical weapons.

"Both the minister [Turkey Foreign Minister Ahmet Davutoglu] and I saw eye to eye on the many tasks that are ahead of us, and the kinds of contingencies that we have to plan for, including the one you mentioned in the horrible event that chemical weapons were used. And everyone has made it clear to the Syrian regime that is a red line for the world," Clinton said at the time.

But today, he made sure to emphasize that all major players in the region have been informed of where his line falls.

"We have communicated in no uncertain terms with every player in the region that that's a red line for us and that there would be enormous consequences if we start seeing movement on the chemical weapons front or the use of chemical weapons," he said. "That would change my calculations significantly."

Obama also made a point of saying that the issue of chemical weapons doesn’t just concern Syria and the United States, but also allies in the region including Israel.

While the international community would still like to see a political solution to the violence in Syria, Obama said, “at this point the likelihood of a soft landing seems pretty distant."

The U.S. will most likely provide even more monetary humanitarian assistance to help those fleeing the Syrian conflict on top of the $82 million the government has already given. According to USAID, the United Nations “estimates that approximately 2 million people in Syria are in need of humanitarian assistance, approximately 1 million people are internally displaced, and more than 140,000 people have fled to the neighboring countries of Jordan, Turkey, Lebanon, and Iraq.”

President Obama and his Russian counterpart, Vladimir Putin, met on Monday for the first time since the violent uprising in Syria began to discuss possible actions to limit further bloodshed in the meeting.

Putin, who reassumed the presidency of Russia earlier this year, met with Obama in bilateral talks that stretched for some time; both leaders were in Mexico for this week's G-20 summit.

Both leaders said they found common ground on the conflict, but shed little light on the steps upon which they agreed were needed to mount the violence between the Syrian people and the country's rulers. Putin is an ally of Syrian President Bashar al-Assad and has generally resisted imposing more sanctions on that regime.

Putin shared just two sentences on the issue of Syria, speaking through a translator: “We also discussed international affairs, including the Syrian affair. From my perspective, we've been able to find many commonalities pertaining to all of those issues.”

Obama said the leaders “agreed that we need to see a cessation of the violence, that a political process has to be created to prevent civil war, and the kind of horrific events that we've seen over the last several weeks, and we pledged to work with other international actors including the United Nations, [UN Special Envoy] Kofi Annan, and all the interested parties in trying to find a resolution to this problem.”

At a press briefing after the two leaders met, Ben Rhodes, deputy national security adviser for strategic communications, stressed that Putin supports a political transition in which Assad loses power, even if the Russian president is not as vocal about such views as other leaders. 

“It's true the Russians have not publicly issued the same type of call for Assad to step down,” Rhodes acknowledged.

During the meeting, President Obama also said the two leaders discussed negotiations with Iran over its nuclear program, stressing the “shared approach” among members of the P5+1, a group that includes the U.S., Britain, Russia, France and China plus Germany, in their dealings toward the Iranian regime.

That emphasis on a shared approach highlights Russia's opposition to unilateral sanctions against Iran, such as the ones installed by the United States against countries that do business with Iranian oil companies. Just last week, Russian foreign minister Sergey Lavrov said during a press conference in Iran that “unilateral sanctions by others will never have a positive and constructive outcome.”

Obama also made a passing reference to an issue that has been a key factor in US-Russia relations, but over which the president recently got into domestic political hot water: missile defense.

During a meeting in March with then-Russian president Dmitry Medvedev, Obama was caught on a hot microphone saying he would have “more flexibility” on the missile shield issue after the November elections, to which Medvedev uttered the now-infamous response, “I will transmit this information to Vladimir.” Republicans pounced on the exchange, saying it represented American weakness on the international stage.

But today, Putin gave little indication of just what was transmitted, as the only thing either leader said on the topic was that it was discussed among a “range of strategic issues,” according to Obama, and that they “resolved to continue to work through some of the difficult problems involved there.”

The interaction between the two leaders, meeting for just the second time, was perceived by the press in the room as somewhat chilly. As the group of journalists was ushered out of the room, “Messrs. Obama and Putin remained seated, their interpreters had stepped away, sitting side-by-side on the other side of the room -- and they just stared straight ahead. No interacting or chit chatting,” one pool reporter wrote.

But administration officials later urged observers not to read in to the encounter.

“This isn’t the first Body Language-Gate that we've had with the Russians,” Rhode said, noting that relations between Obama and Medvedev, who are considered to have a more friendly relationship than that between Obama and Putin, have also been perceived as frosty.

“That's just his style. I would encourage you not to read too much into that as part of relationship,” said U.S. ambassador to Russia Mike McFaul, also at the briefing today.