It apparent that the U.S. government has counseled the Siniora government to avoid a compromise to end the stalement with the opposition and to end the demonstrations that have shutdown central Beirut. The U.S. motive is not hard to read: since Hezbollah is seen as a proxy of Iran, any deal that benefits Hezbollah's standing will buttress Iran's role in Lebanon. This black and white thinking obscures the fact that there are real political issues at stake, and they go beyond the issue of the international tribunal that will be assembled to try any case against the accused assasins of Rafiq al-Hariri. Hezbollah, Amal, Michel Aoun's FPM, and a variety of other groups including communisits and the secular-nationalist (and pro-Syrian) SSNP, are demanding structural political in the Lebanese political system. Indeed, the alliance between Aoun and Hezbollah is explained in significant measure that they both represent constituencies that see themselves as disenfranchised.
Thus, Siniora's suggestion that the U.S. pressure Israel to withdraw from Shabaa is unlikely to break the logjam for two reasons: the structural political issues will remain, and an Israeli withdrawal from Shabaa will still leave Lebanon, and particularly southern Lebanon with a security problem, namely this is the part of Lebanon that has suffered repeatedly from Israeli incursions, attacks and invasions. The people who live in the South have a legitimate claim that they want to be defended. They ask who will do that? It will not be UNIFIL, and it will not be the Lebanese army. So who? Many of them answer "Hezbollah". Like it or not, that is a fact.
Finally, Siniora's argument that movement on the Palestinian-Israeli front is urgently needed is well taken, but in it current chiliastic mood it is not clear that Washington hears very well.