NBC News has obtained a copy of a seven-page letter from House Oversight Chairman Darrell Issa to Barack Obama that raises the stakes in the stand-off between Congress and the attorney general.

In the letter, Issa challenges the president's assertion of executive privilege over documents sought by the committee in the "Operation Fast & Furious" investigation.

Issa requests the president provide a formal, legal justification for the privilege claim and a list of specific documents covered by it.

Issa points to case law that maintains executive privilege is reserved for direct presidential decision-making.  

The California Republican ratchets up the pressure by stating that either the president's "most senior advisers were involved in managing Operation Fast & Furious ... and the fallout" or the White House is asserting "a presidential power that you know to be unjustified solely for the purpose of further obstructing a congressional investigation."

The letter includes the president's own public statements that neither he nor Holder knew about or authorized the operation. 

Issa asks why and the attorney general was offering certain documents last week with the condition that the contempt citation be dropped but the next day those same documents were shielded by executive privilege.  

The chairman says there has been no explanation for how Holder could tell the president that releasing the documents would result in "significant damaging consequences" only hours after saying he could provide them to congressional leaders if contempt was off the table.

Rep. Issa: No evidence of White House cover-up in 'Fast and Furious' gun-running case

The chairman goes through the history of the case, the death of border agent Brian Terry and reminds the president that Attorney General Holder provided false information to Congress on Feb. 4, 2011 in a letter that denied the gun operation permitted illegally bought weapons to cross into Mexico.

The Justice Department retracted that denial months later. Issa pointedly states that lying to Congress is a crime itself and says the subpoenaed documents pertain to Holder's denial and internal communications that brought about the subsequent correction.  

In a new request, Issa also asks for any communications between the White House and Justice between the date of the false denial and June 18, 2012, the day before privilege was asserted.

Issa rejects criticism that the contempt vote is purely political.  He complains that Holder referred to the committee's action as an "election-year tactic."

Issa writes that "nothing could be further from the truth. This statement not only betrays a total lack of understanding of our investigation, it exemplifies the stonewalling we have consistently faced."

Still, the House Oversight Chairman tells the president he is "hopeful the Attorney General will provide the specified documents so that we can work towards resolving this matter short of a contempt citation."