On Tuesday, senior State Department officials provided the first detailed timeline of the attack and the movements of slain U.S. Ambassador Chris Stevens, and indicated that there had not been a protest preceding the attack, as had been previously reported.

The Romney campaign said there remained "many questions about whether or not the Administration properly heeded warnings, provided adequate security, or told the American people the whole truth in the aftermath of the attack."

"On an issue of this importance, nothing short of full and complete candor is acceptable," Chen said. "We can't learn from our mistakes if we don't undertake an honest, transparent effort to assess them."

At the White House press briefing on Wednesday, press secretary Jay Carney said officials had initially spoken "based on the facts we knew at the time" and that the White House has always insisted "this was an ongoing investigation."

"This is a moving picture," Carney said, adding that "our sole interest — the president's sole interest — is to find out exactly what happened."