The transition "must be meaningful, it must be peaceful and it must begin now," Obama said at the White House after speaking with the Egyptian president by telephone for 30 minutes.

In Cairo, Mubarak said he would not seek re-election in September, but he rejected protesters’ demands that he step down immediately, a halfway concession that did not calm his critics.

Obama’s comments suggested that September might not be soon enough. He did say that Mubarak "recognizes that the status quo is not sustainable and that a change must take place."

Obama said the transition should include a broad spectrum of Egypt’s political factions.

He said that demonstrators, who have been mostly peaceful, have been "an inspiration to people around the world."

"To the people of Egypt, especially the young ones, I want to be clear, we hear your voices," Obama said. "I have an unyielding belief that you will seize your own destiny."

Obama suggested the United States would take a hands-off approach to the change in leadership.

"It is not the role of any other country to determine Egypt’s leaders," he said. However, he said it was essential that the process "lead to elections that are free and fair" and responsive to the aspirations of the Egyptian people.

"Throughout this process, the United States will continue to extend the hand of partnership and friendship," he said.

Obama said there would be "difficult days ahead" and many questions remain. But, he added in his brief remarks, "I am confident the people of Egypt will find those answers."