Speaking at the White House following a telephone call with Mubarak, Obama said the Egyptian president -- who announced Tuesday he will not run for re-election -- recognizes "the status quo is not sustainable and that a change must take place."
Referring to massive anti-Mubarak demonstrations that have persisted for more than a week in Cairo and other Egyptian cities, Obama noted Egypt has undergone "many transformations" in its history.
"The voices of the Egyptian people tell us that this is one of those moments," he said.
"I indicated (to Mubarak) my belief that an orderly transition must be meaningful, it must be peaceful and it must begin now," Obama said.
The U.S. president reiterated that the United States opposes violence and commended the Egyptian military "for the professionalism and patriotism that it has shown thus far in allowing peaceful protest while protecting the Egyptian people."
He urged the military to "continue its efforts to help ensure that this time of change is peaceful."
Obama repeated an assertion the U.S. government has made several times during the protests in Egypt, that freedom of assembly and speech and access to information are universal human rights.
He said the Egypt's power transition must include "a broad spectrum of Egyptian voices and opposition parties, elections that are free and fair and a government grounded in democratic principles and responsive to aspirations of Egyptian people" but he acknowledged "there will be difficult days ahead."
The 82-year-old Mubarak, whose regime has lasted nearly 30 years, said Tuesday he would remain in office until elections are held this fall.