President Barack Obama tried the impossible: winning the hearts and minds of Egyptians furious with their autocratic ruler while assuring a vital ally that the United States has his back.

The four-minute speech Friday evening represented a careful balancing act for Obama. He had a lot to lose by choosing between protesters demanding that Egyptian President Hosni Mubarak step down from a government violently clinging to its three-decade grip on the country.

"The United States will continue to stand up for the rights of the Egyptian people and work with their government in pursuit of a future that is more just, more free and more hopeful," the president said.

Yet he offered no ultimatum or specific demand, saying instead that Mubarak had a "responsibility to give meaning" to his pledges of better democracy and more economic opportunity.

The U.S. response is challenged by a massive mismatch in the perception and reality of its power. Despite spending billions in Egypt to establish a bulwark of American influence in the Middle East, the U.S. has little capacity to determine whether the 82-year-old Mubarak weathers the protests or is toppled, analysts and past administration officials say.

In his first television appearance since protests erupted three days ago, Mubarak said Friday he asked his Cabinet to resign. He said he would reconstitute it yet outlined no concrete democratic reform. He also defended the brutal crackdown on protesters, who've faced baton beatings, water cannons, rubber bullets and tear gas.

Speaking shortly after, Obama didn't endorse regime change. Nor did he say that Mubarak's announcement was insufficient. Instead, he said he personally told Mubarak to take "concrete steps" to expand rights.

Does that mean that Mubarak should step down after three decades in power? Should he announce that he won't run again for president? What about constitutional changes? Is it time to scrap emergency laws in place since 1981?

Administration officials would not say.

Obama's address was the most forceful of the day, but it stuck largely to the script already set by Secretary of State Hillary Rodham Clinton and White House spokesman Robert Gibbs.

"What will eventually happen in Egypt is up to Egyptians," Clinton said, noting that the Egypt government could ease tensions by rapidly introducing democratic reform. "That moment needs to be seized, and we are hoping that it is."

"The legitimate grievances that have festered for quite some time in Egypt have to be addressed," Gibbs said. "And violence is not the response."

The reality is that the United States can do little to control or direct the anger in the Arab world unleashed two weeks ago when Tunisia chased its long-time ruler from power. Yet the U.S. can do severe harm to its own interests by coming out too forcefully for or against the uprising.

Washington's perceived ability to pick and choose governments is limited to a very few places. It does not wield that power in the Middle East, where Islamic parties completely opposed to the United States are often the most likely democratic alternatives.

"This is the most serious foreign policy crisis the administration has faced," said Aaron David Miller, who worked two decades at the State Department and is now a scholar at the Woodrow Wilson Center. "The paradox is, there is little if anything the administration can do."

That doesn't mean it won't try.

The White House said earlier Friday it would review the $1.5 billion in annual aid to Egypt, an unsubtle warning that it still has some pull with Cairo.

The State Department issued an unusual warning to Americans to avoid all but essential travel to Egypt at the height of the winter tourism season.

"The U.S. doesn't believe revolutions are the way to go," said Robert Danin, a senior fellow at the Council on Foreign Relations and a State Department specialist on the Middle East under President George W. Bush. "Revolutions are violent. They have unanticipated outcomes."

Still, rhetoric matters. After spending billions backing its few Arab friends, the U.S. has damaged credibility in the Arab world, leaving a narrow space for Washington policymakers.

Without a bold statement of solidarity, it's tough to see how the United States will gain the sympathy of Egyptian protesters fighting a security apparatus that has worked closely with American counterparts and may be using U.S. equipment to repress them.

Obama aimed high: "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 and the United States will stand up for them everywhere."

But he tempered the bold idealism of a world of universal rights with a strong plea for peaceful protests. And he was clear that Mubarak's government still had some U.S. support. "We are committed to working with the Egyptian government and the Egyptian people," Obama said.

The need for balance is obvious. Completely alienating Mubarak would be a disaster for the U.S. if his government weathers the storm, possibly harming cooperation in the Mideast peace process or on counterterrorism.

Scott Carpenter, a fellow at the Washington Institute for Near East Policy, said the United States will have more options once it becomes clear which side will prevail. "We cannot dictate anything," he said.

Others decried what they deemed a reactive approach to U.S. foreign policy.

"We don't side with the regime or the protesters when it matters," said Michael Rubin, a scholar at the American Enterprise Institute. "By being so cautious and cynical, we end up not winning the hearts and minds of either side."


EDITOR'S NOTE _ Bradley Klapper covers foreign affairs for The Associated Press.