For nine days, as European and United Nations officials have called urgently for a cease-fire in Gaza, the Bush administration has squarely blamed the rocket attacks of the Palestinian militant group Hamas for Israel’s assault, maintaining to the end its eight-year record of stalwart support for Israel.

Mr. Bush, in his weekly radio address on Saturday, said the United States did not want a “one-way cease-fire” that allowed Hamas to keep up its rocket fire, and Vice President Dick Cheney on Sunday echoed the point, declaring that only a “sustainable, durable” peace would be acceptable.

Many Middle East experts say Israel timed its move against Hamas, which began with airstrikes on Dec. 27, 24 days before Mr. Bush leaves office, with the expectation of such backing in Washington. Israeli officials could not be certain that President-elect Barack Obama, despite past statements of sympathy for Israel’s right of self-defense, would match the Bush administration’s unconditional endorsement.

“Obviously Bush, even by comparison with past U.S. presidents, has been very, very pro-Israel,” said Sami G. Hajjar, a longtime scholar of Middle East politics and a visiting professor at the National Defense University. “Despite Obama’s statements, and his advisers who are quite pro-Israel, the Israelis really didn’t know how he’d react. His first instinct is for diplomacy, not military action.”