Reporting from Washington -- Israel's ground invasion of the Gaza Strip has abruptly increased the stakes for Washington at an awkward moment when President Bush's power is ebbing and his successor is choosing to remain on the sidelines.

The ground assault that began Saturday raises the chances of a sharp increase in casualties, perhaps on both sides, that would heighten international pressure on the United States to intervene in an attempt to end the conflict. World powers are already clamoring for Washington to play its traditional lead role in finding a way out of the crisis.

But Washington is in transition.

Steven Cook, Middle East analyst at the Council on Foreign Relations, said the invasion comes at "this weird moment the president's powers are diminished and his successor is not yet engaged."

Although Bush administration officials insist that they have been pressing hard diplomatically, questions remain about whether they have the leverage to produce a settlement -- or even want one at a moment when there is no clear victor. If the fighting ends in ambiguity, it could be read around the region as a victory for the radical Hamas movement that controls Gaza, as well as its supporters in Iran.

For its part, the Obama team, which has laid out its intentions on the financial stimulus package being debated in Congress, says it will continue to defer to the Bush administration on this leading foreign policy issue.

"There is one president at a time, and we intend to respect that," said Brooke Anderson, Barack Obama's chief national security spokeswoman, who added that the president-elect is "closely monitoring" events.

Because of the conflict in the Middle East, Secretary of State Condoleezza Rice will not be traveling to Beijing as expected.

Instead, it was announced Sunday, Deputy Secretary of State John D. Negroponte will travel Wednesday to meet with Chinese officials and attend events commemorating the 30th anniversary of the establishment of diplomatic ties between the United States and the People's Republic of China.

David Makovsky of the Washington Institute for Near East Policy said that, from his perspective, "nobody's home" in Washington even as the ground attack "intensifies the conflict and, with that, more and more people are now going to be looking to Washington."

There have been some signals that Israel, which generally prefers short wars, wants to wrap up the fighting before Obama takes office Jan. 20. But now, with Israeli Defense Minister Ehud Barak warning that the incursion "will not be short," there appears to be a growing possibility that the president-elect will be faced with a shooting war to contend with as soon as he is sworn in.

Obama may have hoped that he could begin his term dealing with Arab-Israeli issues from some middle ground. But the deepening crisis will make it difficult for him to avoid taking a position that will upset one side or the other.

The Bush administration has repeatedly put the onus on Hamas to take steps to end the fighting by stopping its rocket attacks on Israel. Officials have declined in recent days to take a position on whether the ground invasion was justified, and whether Israel's response has been "proportional."

Vice President Dick Cheney said Sunday that Israel "didn't seek clearance or approval from us, certainly" before the ground invasion, but did not say whether Israel informed its ally of its plans beforehand.

Senate leaders from both parties described Israel's actions as understandable.

"I think what the Israelis are doing is very important," Senate Majority Leader Harry Reid said. "I think this terrorist organization, Hamas, has got to be put away."