Ambassador Thomas Pickering was chairman of the Accountability Review Board chairman REUTERS/Chris Usher/ CBS News/Handout via Reuters (UNITED STATES - Tags: Ambassador Thomas Pickering (CBS News/ Handout via Reuters)

The House Oversight and Government Reform Committee announced Monday that it was expanding its investigation of the assault on the American mission in Benghazi, Libya, and

will interview the two men who led the State Department review of the U.S. response to attack.

The committee said it is asking former ambassadors Thomas Pickering and Adm. Mike Mullen, who co-chaired the State Department Benghazi Accountability Review Board, to submit to formal, transcribed interviews with committee investigators in anticipation of a public hearing on the investigation.

Pickering and Mullen have said they are willing to speak further with the House committee about their investigation.

The announcement came while President Obama was holding a press conference with the visiting British Prime Minister David Cameron.