WASHINGTON - The United States bluntly urged Egyptian President Hosni Mubarak on Wednesday to make political reforms in the face of protesters demanding his ouster, marking a pivot in its stance toward a key Arab ally.

US Secretary of State Hillary Clinton delivered the message at a news conference with the foreign minister of Jordan, another Arab country that watched the ouster of Tunisia's president in a popular revolt two weeks ago.

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Police in Cairo fought with thousands of Egyptians who defied a government ban on Wednesday to protest against Mubarak's 30-year-old rule, firing tear gas at the crowds and dragging away demonstrators.

The revolt in Tunisia has prompted questions about the stability of other Arab governments and initially dragged down equity, bond and foreign exchange prices in parts of the region, notably Egypt.

Tunisia's veteran strongman Zine al-Abedine Ben Ali was swept from power on Jan. 14 after weeks of protests.

Clinton minced no words, suggesting Egypt's government had to act now if it wanted to avert a similar outcome and urging it not to crack down on peaceful protests or disrupt the social networking sites that help organize and accelerate them.

"We believe strongly that the Egyptian government has an important opportunity at this moment in time to implement political, economic and social reforms to respond to the legitimate needs and interests of the Egyptian people," Clinton said in a statement with Jordan's Nasser Judeh at her side.

"We urge the Egyptian authorities not to prevent peaceful protests or block communications including on social media sites," Clinton told reporters in the most blunt comments to date by the United States urging Mubarak to undertake reforms.

Genuine change

Robert Danin of the Council on Foreign Relations think tank said Clinton's remarks for the first time appeared to make clear what the United States wants to see in Egypt: genuine change that originates from the government rather than a dramatic overthrow as occurred in Tunisia.

As the first Arab state to make peace with Israel, Egypt has much greater strategic importance to the United States than Tunisia. Egypt has long received major US aid and supported Washington's efforts to promote a wider Arab-Israeli peace.

"This is not a walking away from the alliance with Egypt in any way but, at the same time, putting the Egyptian government on notice that changes are going to have to come pretty quickly," Danin said.

"It is trying to lay out a way there can be managed change if the regime is responsive to the people," he said. "It (the Obama administration) doesn't want to see the means adopted in Tunisia - which would necessitate the leadership to flee."

The White House took a similar stance, making clear that it was monitoring events closely and that it fully supported the Egyptian people's right to peacefully protest.

"We are supportive of the universal rights of assembly (and) speech. ... We would stress quite clearly for all involved that expressions should be free from violence," White House spokesman Robert Gibbs told reporters aboard Air Force One.

"This is an important time for the government to demonstrate its responsibilities to the people of Egypt in recognizing those universal rights," Gibbs said.