Later during the hearing, Panetta was more specific: "I've received reports that possibly Mubarak might do that [step down tonight]. We are continuing to monitor the situation...we have not received specific reports."
"I would assume that [Mubarak] would turn over more of his powers to [Vice President Omar] Suleiman...[who would] direct more of the reforms that need to take place...," Panetta added.
President Barack Obama reiterated his support for an "orderly transition" of power in Egypt during a speech Thursday afternoon at Northern Michigan University focused on job creation and expanding high-speed rail and infrastructure initiatives in the country.
"We are following today's events in Egypt very closely, and we'll have more to say as this plays out," Obama said. "What is absolutely clear is that we've been witnessing history unfold...it's a moment of transformation that is taking place because the people of Egypt are calling for change and they've turned out in extraordinary numbers -- people of all ages and all walks of life."
"Going onward we want those young people and all Egyptians to know ..that America will do everything we can to support an orderly transition in Egypt," he said.
Before the speech, Obama responded only briefly to questions on whether Mubarak is planning to step down Thursday night.
"We're going to have to wait and see what's going on," he told reporters during a surprise lunch stop.
National Security Adviser Tom Donilon briefed the President at the White House this morning, and Obama is in regular touch with National Security Council staff no matter where he is, according to White House press secretary Robert Gibbs.
Gibbs, who is taking his last official Air Force One trip before leaving his job at the end of the week, said the situation remained fluid but would not directly comment on Panetta's statements.
"I am watching much of what you're watching," Gibbs told reporters traveling with the President on Air Force One. "We're watching, I think, a very fluid situation. What we're looking for and what the president spoke about many days ago remains our priority: an orderly transition to a free and fair election. What we're looking for remains unchanged."
Gibbs cautioned that he didn't want to "prejudge what might happen later today" and pledged that the President would "react as the situation warrants" and was prepared to do so even while traveling in Michigan.
"I think we've been clear in the many preceding days that what we have wanted to see and most importantly what the people of Egypt wanted to see was irreversible change, and we'll monitor throughout the day what is happening today," he said.
Asked whether Suleiman would indeed take control, Gibbs said he was "not going to get in over the tips of my skis on this one."
"I will endeavor to get us the best information throughout the day. But I don't want to get into a series of hypotheticals," he said.
During the House intelligence committee hearing, Director of National Intelligence James Clapper pushed back at criticism that the U.S. intelligence community did not predict the uprising and unrest in Egypt before it broke out.
"The intelligence community has been aware of the tensions in Egypt and has consistently reported on them...but we are not clairvoyant," he said.
Under questioning from Rep. Mike Rogers (R-MI), who chairs the panel, Clapper gave the intelligence community's record on Egypt reporting a "B+, not an A-" and said he would tell the committee why in closed session.
Separately, at a House Foreign Affairs Committee hearing, Deputy Secretary of State James B. Steinberg said changes must come to Egypt, noting that the U.S. wants "durable democracies."
"As the President has said, Egypt is not going back to the way it was. We have declared publicly and privately that a peaceful, orderly, and meaningful transition must begin without delay," Steinberg said in prepared remarks.