The White House called on Egypt's government to be "responsive" to its people's aspirations, after thousands took to the streets of Cairo in protests modeled on Tunisia's uprising.
"The Egyptian government has an important opportunity to be responsive to the aspirations of the Egyptian people, and pursue political, economic and social reforms that can improve their lives and help Egypt prosper," said a statement issued late Tuesday.
"The United States is committed to working with Egypt and the Egyptian people to advance these goals," it added.
The strongly worded US statement also underlined US support for basic democratic freedoms in Egypt.
"We support the universal rights of the Egyptian people, including the rights to freedom of expression, association and assembly," the statement said.
The unprecedented protests against Egyptian President Hosni Mubarak's 30-year reign were inspired by similar unrest in Tunisia which forced out president Zine El Abidine Ben Ali after 23 years in power.
The unusually strong White House statement was issued hours after President Barack Obama said in his annual State of the Union address that in Tunisia "the will of the people proved more powerful than the writ of a dictator."
He also insisted that "the United States of America stands with the people of Tunisia, and supports the democratic aspirations of all people."
The statement issued by Obama's office late Tuesday espoused greater democratic freedoms for Egyptians.
"What is happening in the region reminds us that... we have an unyielding belief that all people yearn for certain things: the ability to speak your mind and have a say in how you are governed; confidence in the rule of law and the equal administration of justice; government that is transparent and free of corruption; and the freedom to live as you choose -- these are human rights and we support them everywhere.
Secretary of State Hillary Clinton told reporters in Washington Tuesday that the Egyptian government "is stable and looking for ways to respond to the legitimate needs and interests of the Egyptian people."
Clinton added: "We support the fundamental rights of expression and assembly, and we urge that all parties exercise restraint."
A Twitter microblog message issued by Clinton's spokesman PJ Crowley late Tuesday added: "Egypt must handle protests peacefully and create greater political, social and economic opportunity consistent with people's aspirations."
Tens of thousands of demonstrators took to the streets across Egypt, in the the largest and most significant since riots over bread subsidies shook the Arab world's most populous nation in 1977.
Meanwhile, Twitter confirmed late Tuesday that its website was blocked in Egypt, in an apparent move to thwart protesters using the social network in a campaign to oust President Hosni Mubarak.
Twitter said in a terse "tweet" that it was blocked in Egypt starting about 1600 GMT and that the interruption had derailed Twitter.com as well as applications linked to the service there.
Twitter and Facebook were among Internet social networking services reportedly being used by protesters to share information and coordinate activities.