What can he do? He needs to weigh upon Mubarak to leave. America can not afford a Tahrir Square massacre in its hand; with fighter jets flying low, this seems to be moments away now. The lameness of Hillary Clinton's statement that US does not want a take-over which does not lead to democracy shows that it is yet to make up its mind. This is not a moment of such confusing statement: Does she mean that the US remains with Mubarak and she believes that there is democracy in Egypt?
If Mubarak does not go now, he will fall: With him, he will take the whole US policy in Middle East to grave. This would not remain a matter of freedom and democracy for much longer: The first firing on the crowd will irreversibly seal a war of civilizations finally. On the other hand, forcing Mubarak to leave, and getting him replaced even by another puppet, is the only route left to the US administration.
This is a revolution without an Ayatollah, and this is actually more scary. This may quickly descend into chaos. A more palatable solution is to give the big man a chance to flee and seek sanctuary in Isreal, if Saudis won't take him. But the time has come and we have possibly a few hours, only a few hours. Do any comparison you like, Bay of Pigs or Tehran Embassy, or even Reagan's dithering during the Philippines' People Power revolution, but this is one such moment.