SEOUL, South Korea -- It was a comment not intended for public consumption, and another lesson for President Barack Obama on the importance of being careful about what you say around microphones, especially in an election year.

At the end of a 90-minute meeting between Obama and Russian President Dmitry Medvedev on Monday, journalists rushed in to hear remarks from the leaders about the content of their talks.

Journalists spied the two leaders leaning close together and talking in hushed tones.  According to those in the room, the conversation was difficult to hear but the videotape revealed Obama asking the Russian leader to wait until after the November election before pushing forward on the topic of a planned missile defense shield.

Photos: Obama and Medvedev talk nukes

"Pool" videotape provided more information about the conversation between the two leaders:

Obama: This is my last election…After my election I have more flexibility.

Medvedev: I understand. I will transmit this information to Vladimir. 

While most journalists didn't catch the rest, one Russian reporter managed to record the context with his equipment.

Obama: On all these issues, but particularly missile defense, this, this can be solved but it's important for him to give me space.

Medvedev: Yeah, I understand. I understand your message about space. Space for you...

Obama: This is my last election…After my election I have more flexibility.

Medvedev: I understand. I will transmit this information to Vladimir. 

The planned anti-ballistic shield system has been one of many sore spots between the two world powers in the last few years.

Obama says US can reduce nuclear stockpile

Moscow says it fears the system would weaken Russia by gaining the capability to shoot down the nuclear missiles it relies on as a deterrent. It wants a legally binding pledge from the United States that Russia's nuclear forces would not be targeted by the system.

White House Deputy National Security Adviser Ben Rhodes said the overheard comments were not a departure from the Administration's stated policy and responded to the exchange with the following statement:

“The United States is committed to implementing our missile defense system, which we’ve repeatedly said is not aimed at Russia. However, given the longstanding difference between the US and Russia on this issue, it will take time and technical work before we can try to reach an agreement. Since 2012 is an election year in both countries, with an election and leadership transition in Russia and an election in the United States, it is clearly not a year in which we are going to achieve a breakthrough. Therefore, President Obama and President Medvedev agreed that it was best to instruct our technical experts to do the work of better understanding our respective positions, providing space for continued discussions on missile defense cooperation going forward.”

Medvedev may have told Obama that he understands Obama's predicament, but the White House has been under increasing pressure on the issue.  Last week, the Russian leader gave a downbeat assessment of global security and international relations, saying the "Euro-Atlantic" security community he had hoped to create remained a "myth."

Medvedev, who will be succeeded by Vladimir Putin in May, said Moscow was unconvinced by the argument that the planned missile defense shield was intended as protection against a missile attack by countries such as Iran.

"We have time (for an agreement) but it is running out, and I think that it would be in our mutual benefit to reach mutually acceptable agreements," Medvedev told a security conference.

"The main thing is that we must hear one simple thing - hear it and receive confirmation: 'Respected friends from Russia, our missile defense is not aimed against Russian nuclear forces.' This must be affirmed, not in a friendly chat over a cup of tea or a glass of wine, but in a document."

NBC News' Alicia Jennings and Kristen Welker, and Reuters contributed to this report.