Washington ? The Obama administration got what it wanted when Hosni Mubarak surrendered power. Now it faces another daunting task: coaxing the country’s new military rulers to deliver the genuine democratic reforms they have resisted for decades.

The challenge is to preserve Egypt as a close U.S. ally while also supporting protesters’ demands for a more representative government — probably one that includes a greater role for the Muslim Brotherhood, Egypt’s largest Islamic group.

The U.S. will also try to persuade its other allies in the region to begin their own democratic reforms to avert the kind of protests that toppled Mubarak.

The process brings as much risk as promise for the U.S., which supported Mubarak because he was a reliable ally in a chaotic region who upheld the 1979 peace treaty between Israel and Egypt. The key concern for the White House is that any government that emerges deviates as little as possible from that.

Even as protesters celebrated in Cairo, U.S. officials admitted it was unclear whether the Egyptian military officers now running the country would make good on their promises to undertake real political reform.

U.S. officials acknowledge that events could still easily spin out of control, given Egypt’s lack of experience with democracy, and the clear limits Washington has to influence key players in Cairo.

President Barack Obama began to signal the United States’ priorities shortly after it became clear Mubarak was leaving. In a seven-minute address from the White House, he heralded the protest movement and emphasized to the Egyptian generals now in charge that the U.S. wanted to see a genuine process leading to a more democratic nation.

“This is not the end of Egypt’s transition; it’s a beginning,” Obama said. “But I am confident that the people of Egypt can find the answers and do so peacefully, constructively, and in the spirit of unity that has defined these last few weeks.”

In the short term, U.S. officials want negotiations to sweep away repressive laws and constitutional provisions, replace the regime-dominated parliament and open the power structure to more representative government.

But U.S. officials see reform as a “medium-term” process and favor the slow development of institutions that will give the country a stable and inclusive political process. The task is harder because the Mubarak government has suppressed any parties that threatened its stranglehold on power, essentially forcing the process to start from scratch.

Already, the issue of whether to include Islamist parties in the government is causing friction within the Obama administration.

The administration has said publicly that it believes that the banned Muslim Brotherhood, the Islamist organization that is the largest opposition party, can be brought into the political structure without risk if it will foreswear violence and embrace democratic goals.

Even if Egypt gains a more representative government, as the United States wants, many experts believe it is likely to be more nationalistic than it was in the Mubarak era, and to defy Washington far more often.

“I think that what the administration wants to see is a government with broader representation of the Egyptian society, but one that is continuing to cooperate with the U.S. on security issues, including Israel and counterterrorism,” said Joel Rubin, a former State Department Egypt desk officer who is now deputy director of the national Security Network, a policy analysis organization.

White House officials have argued that Egypt won’t be representative and legitimate unless this large group has some voice.

But administration officials disagree among themselves about the extent of the risk, and American Jewish groups have urged the White House to try to limit the Islamists’ role.