At the same time, the toppling of leaders who preserved a stable, if strained, status quo for decades — Mr. Mubarak, Col. Muammar el-Qaddafi of Libya and Zine el-Abidine Ben Ali of Tunisia — has unleashed powerful and still unpredictable forces that the United States has only begun to grapple with and is likely to be doing so for years.

In the process, diplomats worry, the actions of the United States could even nudge the Arab Spring toward radicalism by angering newly enfranchised citizens of democratic nations.

In the case of Egypt, the administration has promised millions of dollars in aid to support a democratic transition, only to see the military council ruling the country object to how and where it is spent, according to two administration officials, who spoke on the condition of anonymity to discuss diplomatic matters. The objection echoed similar ones that came from Mr. Mubarak’s government. The government and the political parties vying for support before new elections there have also intensified anti-American talk. The officials privately warned of the emergence of an outwardly hostile government, dominated by the Muslim Brotherhood and remnants of Mr. Mubarak’s party.

The upheaval in Egypt has even raised the prospect that it might break its Camp David peace treaty with Israel, with Egypt’s prime minister, Essam Sharaf, telling a Turkish television channel last week that the deal was “not a sacred thing and is always open to discussion.”

The administration, especially Mrs. Clinton, also spent months trying to mediate between Turkey and Israel over the response to the Israeli military operation last year that killed nine passengers aboard a ship trying to deliver aid to Gaza despite an Israeli embargo — only to see both sides harden their views after a United Nations report on the episode became public.

Unflinching support for Israel has, of course, been a constant of American foreign policy for years, often at the cost of political and diplomatic support elsewhere in the region, but the Obama administration has also sought to improve ties with Turkey after the chill that followed the invasion of Iraq in 2003.

Turkey, which aspires to broaden its own influence in the region, has been a crucial if imperfect partner, from the administration’s point of view, in the international response to the fighting in Libya and the diplomatic efforts to isolate Syria’s president, Bashar al-Assad.