American and Israeli officials say Mr. Sharon politely rebuffed Ms. Rice, at least for now.

The exchange, administration officials say, illustrates their new willingness to prod Israel and to get involved in the minutiae of the negotiations. 

A senior official said that in fact more pressure on Israel to stop construction of the fence is certain in coming weeks. "The very fact that Condi Rice raised the issue of the fence with Sharon is significant," said an administration official. "We will be back on this issue if things don't improve." 

The exchange between Ms. Rice and Mr. Sharon also shows, administration officials say, a decision to direct pressure from both the White House and the State Department, which had long been warring over Middle East policy.

The week before Ms. Rice's visit, for example, Secretary of State Colin L. Powell was there pressing for an Israeli withdrawal from the Gaza Strip, even to the point of discussing individual checkpoints on maps of the area.

Diplomats on all sides took note of the careful one-two punch delivered by the two top aides to President Bush. "This is the World Wrestling Federation, and we have a tag team on the Middle East," said a senior State Department official. "For a long time, we've been undercut by the perception that State, the Pentagon and the White House were not aligned. We've worked hard to change that perception."

There was a time in the first months of 2001 when Mr. Bush, Ms. Rice and Mr. Powell all disdained what they said was the obsessive entanglement of the Clinton administration in Middle East negotiations. Administration officials all refused appeals from countries in the region to get more involved.

Now administration officials say their new muscular approach has paid off with the first sign of progress in years — not simply the Israeli withdrawals from Gaza and Bethlehem, but the first tentative cooperation in a long time on security issues and what steps to take next. 

American, European and Middle Eastern diplomats all say that the American pressure has been cautious so far, and will have to become more assertive in coming weeks.

The next test, they say, will be over the administration's willingness to take further steps: stopping installation of the barrier fence, pulling back more forces in the West Bank and dismantling, or at least freezing, settlements there and in Gaza.

Israel is considered unlikely even to consider such steps without seeing the Palestinians crack down first on Hamas and other militant groups — steps that Washington, too, is demanding. The problem is how to arrange further reciprocal steps, and in what sequence — and whether the United States is willing to mediate or orchestrate each new move.

The latest phase of the Middle East peace efforts began in mid-March, with Mr. Bush's formal adoption of the peace plan known as the "road map."

That plan, negotiated with Europe, the United Nations and Russia, calls for reciprocal concessions by Israel and the Palestinians, leading to a Palestinian state in three years. Mr. Bush resisted adopting it until pressure mounted from Prime Minister Tony Blair of Britain on the eve of the Iraq war.

"I saw Bush on TV in the Rose Garden and he looked like someone was holding a gun to his head," said a diplomat in the Middle East, recalling the announcement on March 14 on adopting the plan. "Now he's looking like a seasoned negotiator."

To longtime observers of the Middle East negotiations, the most intriguing aspect of the new internal alignment in the Bush administration is that Mr. Bush has enlisted the White House in a swerve toward a greater willingness to be tough toward Israel, as Ms. Rice was on the Israeli security fence. How much that toughness will be sustained is a matter of conjecture right now.

Until recently, it was the State Department — responding to the views of European and Arab allies whose support was needed for the war with Iraq — that favored seeking concessions from Israel even as the Palestinians were pressed to stop their uprising and attacks.

After Sept. 11, 2001, Mr. Bush plunged into the volatile politics of the Islamic world. Despite engaging with its leaders — whether in Pakistan, Saudi Arabia, Jordan and Egypt, or among the Palestinians — he was said to ally himself more with Mr. Sharon and his supporters, including many at the Pentagon and the office of Vice President Dick Cheney, who emphasize cracking down on terrorism.

By mid-2002, in his most important speech on the Israeli-Palestinian conflict, Mr. Bush declared himself in favor of a Palestinian state. But he said the administration would no longer deal with Yasir Arafat, the Palestinian leader, which delighted Mr. Sharon and his conservative supporters in Israel and the United States.

Throughout this period, administration officials say, Secretary Powell contended that while tough measures were needed on terrorism, the Israeli-Palestinian crisis was political in nature and ultimately needed a political solution. 

This view did not prevail until the Iraqi war and its aftermath, many officials say, when Arab and European supporters of the war took the same view and the installation of Mahmoud Abbas as prime minister made it possible for the United States to resume its contacts with Palestinian leaders.

Along with the evolution of Mr. Bush's thinking has been the evolution of the role played by Elliott Abrams, a conservative former Reagan administration official recruited by Ms. Rice last year to direct Middle East affairs at the National Security Council staff.

At first, the Abrams appointment stirred consternation at the State Department. Mr. Abrams, a combative advocate of Israel's interests, had after all opposed the Oslo peace efforts in the early 1990's, warning that Mr. Arafat could not be trusted.

Mr. Abrams is still said to take Israel's side on such issues as the need for a hard line on Hamas and other Palestinian militant groups, and tough demands on the Palestinian leadership to stop the incitement of violence. 

But earlier this year, Mr. Abrams was among those around Mr. Bush advocating that Israel accept the road map peace plan, in the face of Israeli objections and opposition by many American conservatives, including Tom DeLay, the House majority leader, and several Jewish and evangelical Christian groups.

Mr. Abrams has also recently questioned the Israeli policy of proceeding with the fence, officials and diplomats say, on the ground that it is provocative to Palestinians. 

A top official said Mr. Abrams now advocates direct economic aid to the Palestinian Authority to shore up Mr. Abbas and Salam Fayyad, the Palestinian finance minister.

Among other things, this change has dismayed some hard-line supporters of Israel in the United States. A group of 25 Jewish leaders met with Ms. Rice last Wednesday, and, while many were supportive, some of the conservatives questioned her skeptically about the latest policies, in particular the decision to provide more aid to the Palestinians.

Aides to Mr. Sharon in Israel say that, although Israel disagrees with some recent American suggestions, such as the one to stop construction of the fence, relations remain cordial.

Mr. Sharon has been described in the past as disdainful of the peace plan, declaring it to be a product of the State Department and its thinking.

He and his aides raised nearly 100 objections to it, then reduced these to 14 and then accepted the document with the vague promise that Israel's concerns would be taken into account as the plan was carried out. 

Early in the Bush administration, Mr. Sharon made a point of trying to forge ties with Mr. Bush's conservative inner circle, particularly I. Lewis Libby, Vice President Cheney's chief of staff.

In an unusual step, he circumvented the State Department by sending a private emissary, Arie Genger, a former business partner, to the White House but not the State Department, said several officials knowledgeable about the subject. Now, they say, Mr. Genger has slipped into the background but is still involved as a "back channel" to the administration, they say. 

Israelis assert that, despite a difference of views on some matters, the Bush administration and Mr. Sharon's team have close ties. "We don't agree on everything, that's for sure," said an Israeli official. "But if we disagree, we disagree, and we don't feel pressure on issues of our security."

As for the administration's micro-managing of the process, few experts are surprised at such a turn of events. 

"Guess what?" said Dennis Ross, the former Middle East negotiator in the Clinton years. "Once you're into it, you have to get into the details. You can't deal with the Middle East at the level of a slogan. You deal with it in ways that reflect the reality on the ground."