ASHINGTON, June 10 — President Bush sharply rebuked Prime Minister Ariel Sharon's government today after it tried to kill a Palestinian militant leader, asserting that the Israeli action undermined recent Middle East peace efforts.

The White House also said that several administration officials who were known to have had differences on the Middle East came together in what one official called a "full-court press" to convey the same message of American displeasure to Israel.

Not since Israel sent troops into major Palestinian cities following a round of suicide bombings more than a year ago has such criticism been directed at Jerusalem.

Administration officials said, however, that they also pressed the new Palestinian prime minister, Mahmoud Abbas, to rein in violence on the Palestinian side. The dual approach was a continuation of Mr. Bush's appeals to both sides last week in Egypt and Jordan.

Administration officials said they did not feel that the Israeli airstrikes on Dr. Abdel Aziz Rantisi, a top leader of the militant group Hamas, had been deliberately intended to undermine peace negotiations or to sow dissension in the Bush administration between advocates and critics of Israel's policies.

But the administration was clearly jolted by what Middle East experts say has been a familiar pattern of seeming breakthroughs — like Mr. Bush's meetings with Mr. Sharon and Mr. Abbas in Sharm el Sheik, Egypt, and Aqaba, Jordan, last week — followed by acts of violence apparently intended to undermine peace efforts.

Mr. Bush made his comments at a meeting with the president of Uganda, Yoweri Museveni, several hours after Israeli helicopter gunships carried out the missile attacks in Gaza, including the failed effort to kill Mr. Rantisi. "I am troubled by the recent Israeli helicopter gunship attacks," Mr. Bush said. "I regret the loss of innocent life. I'm concerned that the attacks will make it more difficult for the Palestinian leadership to fight off terrorist attacks. I also don't believe the attacks help the Israeli security."

The White House said that among the officials reaching out to Israelis and others in the region were Condoleezza Rice, the national security adviser; Elliott Abrams, the hawkish director of Middle East affairs on the national security staff; and William J. Burns, assistant secretary of state for Near Eastern affairs and a diplomat with close ties to the Arab world.

Secretary of State Colin L. Powell criticized Israel from Buenos Aires, his latest stop in a trip through Latin America.

Fearing that the peace talks might now be derailed, the administration scheduled separate meetings on Wednesday between the United Nations Secretary General, Kofi Annan, and Ms. Rice and Mr. Powell.

Arab and European diplomats said that the episode today posed a new challenge for Mr. Bush, putting increased pressure on him to get even more involved in talks with Mr. Sharon and the Palestinians.

In the view of American and other diplomats, Palestinian attacks on Israeli soldiers over the weekend — carried out in an unusual coordinated operation by Hamas, Islamic Jihad and the Al Aksa Martyrs Brigade — represented an effort to undermine Mr. Abbas and also provoke the kind of Israeli retaliation that came today.

A diplomat involved in the peace negotiations said that Israel's action was "a slap in the face for Bush," and that the President had no choice but to appeal to Israel for some restraint if the administration's peace plans are to be salvaged.

A senior White House official said that Mr. Bush remained determined not to get involved in the day-to-day ups and downs of Middle East peace efforts and that he therefore refrained from calling any of the leaders himself today.

"There are going to be all kinds of problems in the Middle East," said the official. "If the president intervenes every time, the parties will never be empowered enough to take steps themselves. The parties in the field have to have the ability to fix things themselves."

Mr. Bush and his aides still faced the question of what to do about Yasir Arafat, the Palestinian leader, who administration officials believe is working to sabotage Mr. Abbas.