After decades of American policy predicated on backing reliable, albeit repressive regimes in Egypt and Saudi Arabia, Barack Obama has begun signalling more sympathy with the aspirations of protesters in the Arab street, a shift that could put the president on the right side of history or doom his relations in the Middle East.
It's a "move charged with great danger," said Leslie Gelb, president emeritus of the Council on Foreign Relations. "The Obama team is tilting slightly away from Hosni Mubarak, Egyptian strongman and U.S. critical ally."
Mr. Obama, in his first public comments as protests rocked Arab capitals, said he had told the Egyptian president to move "forward on reform - political reform, economic reform" and that doing so was "absolutely critical for the long-term well-being of Egypt."
White House spokesman insist the president still regards the Mubarak government as a key ally. But U.S. demands that Cairo and other Arab capitals heed the rising chorus of calls for democracy and accountability signals a push for change and sends a warning to other Arab rulers that they may face the ignominious fate of Tunisia's Zine El Abidine Ben Ali, who fled to Saudi Arabia.
The Obama administration is rapidly recasting its position, apparently trying to stay abreast of the spreading street battles in Egypt, Yemen, Algeria and Jordan.
"The status quo in the Middle East and North Africa is not sustainable," State Department spokesman P.J. Crowley said in a unusually blunt, if self-evident, admission that decades of propping up despots just because they provided oil, handy military bases and could be counted on as firm friends in a region filled with implacable enemies was coming to an untidy end.
"This isn't a choice between the government and the people of Egypt," Mr. Obama's spokesman Robert Gibbs said as massed crowds faced hordes of security police in Cairo. "This represents an opportunity for President Mubarak and the government to demonstrate its willingness to listen to its own people."
But if the aged and ailing Mr. Mubarak, who has ruled for 30 years, doesn't listen to Egyptians, then Mr. Obama will be forced to make a choice.
That too is a shift. For decades, successive American governments have hammered unfriendly Arab regimes for being autocratic, dictators with brutal histories of repressing their own people. But Washington's allies in the region mostly got a break. The benchmark wasn't a regime's repressiveness, but whether it was America's friend or foe.
Even the waves of pro-democracy demonstrators who challenged the rulers in Tehran after a stolen election in 2009 got scant support from Mr. Obama.
"It is not productive, given the history of U.S.-Iranian relations, to be seen as meddling," the president said then.
This time, while senior administration officials are at pains to point out that Tunisia - a small, weak, relatively rich and homogeneous state - can hardly be the model for change in Egypt, it could be the igniter that sets off a conflagration of change.
Egypt, the most populous and powerful Arab state, the key U.S. ally in the region and the first nation to make peace with Israel, may define whether the Tunisian spark splutters and dies or spreads.
But there are grave risks, especially because it is impossible to anticipate the outcome when strategically allied governments are toppled.
For the massed crowds in the streets and their mostly unknown leaders, belated and tepid backing from America after generations of silence may fail to build a secure future friend.
"In rotten regimes that fall to street mobs, the historical pattern has been moderates followed by new dictators," Mr. Gelb warned, pointing to the 1979 Iranian revolution that toppled the Shah - then America's key ally in the region.
Meanwhile, if Mr. Mubarak and other Arab rulers manage to crush the current wave and survive, the apparent willingness of Washington to abandon long-term allies at the first signs of protest will make future relations chilly at best. In the struggle against Islamic extremism and Mr. Obama's hopes of reviving a Palestinian-Israeli peace, both Egypt and Saudi Arabia remain critical players.