A recurring issue is whether changes were made to the intelligence material at the request of the White House or for political reasons. Lieberman said Morell told him that was not the case.
"The acting director of the CIA said whatever changes were made in the original talking points before they were given in unclassified form to the House Intelligence Committee and to Ambassador Rice were made within the intelligence community," Lieberman said.
Despite lingering questions over her public comments after the Benghazi attack, Rice has emerged as the top candidate on a short list of possible successors to Clinton, with Senate Foreign Relations Committee Chairman John Kerry, D-Mass., seen as her closest alternative.
The strong statements from the three senators clouded Rice's prospects only two days after Republican opposition seem to be softening. Rice planned meetings on Wednesday with Sen. Bob Corker of Tennessee, who is in line to become the top Republican on the Foreign Relations Committee, and Sen. Susan Collins, R-Maine.
Corker said Tuesday that he had concerns with a possible nomination.
"When I hear Susan talk she seems to me like she'd be a great chairman of the Democratic National Committee," Corker said. "There is nobody who is more staff supportive of what the administration does. That concerns me in a secretary of state."
Sen. James Inhofe, R-Okla., who had indicated late Monday that Rice perhaps had been unwittingly used by the administration, said in a statement Tuesday that Rice is unfit for the top diplomatic post.
"It is now clear that she willingly misled the American public five different times in the days after the attack," Inhofe said. "And for months after the attack she failed to acknowledge, until today, that her account of what happened was deeply and fundamentally flawed."
A senior Senate aide said the administration was sounding out moderate members of the Foreign Relations Committee, such as Corker and Sen. Johnny Isakson, R-Ga. Assessing the prospects for Rice before Obama makes any announcement would avoid the embarrassment of a protracted fight with the Senate early in the president's second term and the possible failure of the nominee.
On talk shows the weekend following the attack, which took place on the 11th anniversary of 9/11, Rice was given talking points that described the attack as a spontaneous protest of the film, even though the Obama administration had known for days that it was a militant assault.
Republicans called her nomination doomed, leading to a vigorous defense of her by Obama in his first postelection news conference. Since then, GOP lawmakers have appeared to soften their views. McCain, who said earlier this month that would he do everything in his power to scuttle a Rice nomination, had said Sunday that he was willing to hear Rice out before making a decision.
Rice, who at 48 is relatively young, has been known to covet the job for years, but was passed over for Clinton in 2009.
Associated Press writers Matthew Lee in Washington and Edith M. Lederer in New York contributed to this report.