JERUSALEM - President Bush sets off this week to celebrate Israel's 60th birthday, but the festivities are likely to be muted by the dimming prospects for brokering regional peace deals during the Republican administration's waning months in power.

On the eve of Bush's trip, Iranian-backed Hezbollah fighters humbled the pro-Western government in Lebanon by seizing large parts of Beirut and unleashing the deadliest clashes since the country's civil war from 1975 to 1990.

An unfolding political corruption scandal has undermined Israeli Prime Minister Ehud Olmert's already questionable ability to secure a peace deal with the Palestinians.

And after a Palestinian rocket killed an elderly Israeli civilian Monday, Israeli leaders warned that a deadly showdown may be on the horizon with the militant Islamist group Hamas in the Gaza Strip.

Combined with Bush's diminishing influence over world events as he nears the end of his second term, the fissures running through the Middle East make any last-minute administration achievements unlikely, said Aaron David Miller, the author of "The Much Too Promised Land: America's Elusive Search for Arab-Israeli Peace."

"This is not an American story right now," said Miller, who served as a Middle East negotiator for Presidents Clinton and George W. Bush. "We are not feared in this region. We are not liked in this region. And we are not respected in this region, so there's not much leverage that we have."

Bush's schedule will take him through the Middle East briar patch that has ensnared his administration since Sept. 11, 2001.

He will celebrate Israel's independence with Olmert and meet with moderate Palestinian leaders.

The president will also visit Saudi leaders who repeatedly have rebuffed the administration's appeals to boost oil production in order to cut gas prices; with Afghan President Hamid Karzai, who's battling emboldened Taliban forces; and with Iraqi leaders central to the administration's final push for stability there.