|More than 1,000 people have been injured across Egypt since protests erupted on Tuesday [Reuters]
The US president has called on his Egyptian counterpart to take concrete steps towards political
reform, and to refrain from using violence against thousands of protesters who have taken to the streets across Egypt.
"I want to be very clear in calling upon the Egyptian authorities to refrain from any violence against peaceful protesters," Barack Obama said in a statement shortly after speaking with Hosni Mubarak by telephone for 30 minutes on Saturday.
"The people of Egypt have rights that are universal. That includes the right to peaceful assembly and association. The right to free speech and the ability to determine their own destiny. These are human rights."
The statement came shortly after Mubarak went on national television to announce that he had dismissed Egypt's government.
Facing the prospect that a cornerstone Arab ally might collapse, the US administration has appealed for Egyptian authorities to halt the crackdown on swelling anti-government protests.
The US has warned citizens to avoid non-essential travel to Egypt and urged Americans in the country to stay put.
An administration official also said on Friday that the $1.5bn US assistance to the country would be reviewed.
The decision is a significant step as the US seeks to balance the desire to maintain stability in the region with a recognition of the unexpected scope and uncertain outcome of the protests aimed at toppling Mubarak's authoritarian government.
Robert Gibbs, White House spokesman, said that the US is "monitoring a very fluid situation".
"The security personnel in Egypt need to refrain from violence, and the protesters should refrain from violence as well," Gibbs said. "The legitimate grievances that have festered for some time have to be addressed by the Egyptian government immediately."
Al Jazeera's Nick Spicer, reporting from Washington, said that the White House has advised "not to let things get out of control because a lot is at stake for the United States".
"I certainly think the Americans are putting a lot of pressure on the Egyptian president to show that he's listening to the people in the street," he said.
The Obama administration has stopped far short of endorsing the protests calling for Mubarak's ouster, an outcome that would shake an already unstable region.
Speaking as street demonstrations rocked Egypt's capital despite a curfew, Hillary Clinton, the US secretary of state, urged calm on both sides.
She said the government must investigate and prosecute any allegations of brutality by security forces.
She also called on Egypt to restore access to the internet and social media sites that have been blocked.
Protests across Egypt on Friday pose the most serious threat yet to the authoritarian Mubarak, a stalwart US ally in the Arab world considered a linchpin for American efforts to forge Middle East peace and tamp down extremism.
His support has been rewarded with billions of dollars in US aid each year over successive administrations.
"These protests underscore that there are deep grievances within Egyptian society, and the Egyptian government needs to understand that violence will not make these grievances go away," Clinton said.
She sidestepped a question on whether the US believed that Mubarak's regime was finished, but said that Washington wanted to work as a partner with both the country's people and government to help realise reform in a peaceful manner.
Clinton said that reform "is absolutely critical to the well-being of Egypt" and urged Mubarak and his government to "engage immediately" with opposition groups and others to make broad economic, political and social changes.
Ileana Ros-Lehtinen, a Republican and chairman of the House Foreign Affairs Committee, said the protests were a sign that the Egyptian peoples' "cries for freedom can no longer be silenced".
She said she was troubled by the "heavy-handed" government response to the demonstrations.
"I am further concerned that certain extremist elements inside Egypt will manipulate the current situation for nefarious ends," she said.
For years, the US has treaded a delicate line with Mubarak, supporting him to further America's Middle East agenda but trying to prod him on human rights and democracy.
While tensions were often evident at public events with US and Egyptian officials, secret diplomatic cables released on Friday by the WikiLeaks website reveal even deeper strains.
"The Egyptians have long felt that, at best, we take them for granted; and at worst, we deliberately ignore their advice while trying to force our point of view on them," Margaret Scobey, US ambassador to Egypt, wrote in a February 9, 2009, memo.
Scobey then urged the US to push the issue of jailed former opposition Al Ghad party leader Ayman Nour - but not with Mubarak: "Mubarak takes this issue personally, and it makes him seethe when we raise it, particularly in public".
The Egyptian government "remains sceptical of our role in democracy promotion, arguing that any efforts to open up will result in empowering the Muslim Brotherhood," Scobey wrote.
She added that despite repeated pressure from the US, overall progress in democratic reform remained slow, and Egypt continued to be suspicious of American interventions on human rights.
In a February 26, 2009, memo, Scobey wrote that the Egyptian government was also unwilling to discuss making domestic concessions in order to receive US aid.
"The Egyptians are proud and will state categorically that they will not bargain for assistance - i.e. they will not barter domestic political concessions in exchange for foreign aid," she wrote.
"The Egyptian reaction to FY2008 [Financial Year 2008] conditionality language was uniformly negative and, with few exceptions, transcended political lines. It did not work."