Infuriated by pressure from Washington, Israel's prime minister summoned the American ambassador.

"You have no moral right to preach to us," he lectured the envoy. "What kind of talk is this, 'punishing Israel'? Are we a vassal state of yours? Are we a banana republic?"

That scolding was 28 years ago, but it echoes as a cautionary tale.

Today, President Obama is pushing a reluctant Israeli government to halt the growth of Jewish settlements and embrace the goal of a Palestinian state. In the 1981 showdown, Prime Minister Menachem Begin held his ground after the Reagan administration suspended a strategic cooperation pact to protest Israel's annexation of the Golan Heights. The territory, captured from Syria in 1967, remains in Israel's hands.

Now, as Obama launches an audacious new effort to make peace in the Middle East, his influence will be limited in similar ways by the regional leaders he must work with.

"We have a 'yes we can' president who believes he can make it happen, but he faces a 'no you can't' reality in a region that has changed for the worst over the past eight years," said Aaron David Miller, a former U.S. Middle East negotiator.

Israeli Prime Minister Benjamin Netanyahu, back in office a decade after his first term, has pledged to resist Palestinian independence. The Palestinian movement is in disarray, with the U.S.-backed leadership in the West Bank at odds with militantHamas rulers in the Gaza Strip over the issue of a permanent peace with the Jewish state.

Egypt and Saudi Arabia, traditional leaders of the Arab world, are ruled by wavering octogenarians who arehesitant to step in as peacemakers.

Meanwhile, Iran's Islamist allies, Hamas in Gaza and Hezbollah in Lebanon,have boosted their arsenals with logistical help from Syria and taken on Israel's army. Both pose a threat to Israel's borders, giving Iran, which the U.S. and others fear is bent on developing nuclear weapons, the power to sabotage any Israeli-Palestinian accord. Iran's ties with Syria and patronage of Hezbollah also help keep Syria and Lebanon formally hostile to Israel.

Against this inauspicious backdrop, the history of the Israeli-Arab conflict offers few examples of fruitful American diplomacy.

Shlomo Avineri, a former Israeli diplomat who teaches political science at Hebrew University, notes that the U.S. has sometimes managed to rein in Israeli military advances when regional stability was at risk, as it did in Egypt at the end of the 1973 war, and has helped secure agreements when Israel and its adversaries were close.

But "absent local political will, and when confronted with a peacemaking project that may take years to complete," he added, "the United States is virtually powerless."

That hasn't discouraged Obama. His special envoy to the region, George J. Mitchell, told Israeli and Palestinian leaders this week that the administration is "fully committed to working toward comprehensive peace throughout the Middle East." He then traveled on to Lebanon and Syria.

The administration has demanded a halt to Jewish settlement growth in the West Bank as a first step to unravel the conflict. By signaling an end to his predecessor's strong tilt toward Israel, Obama is trying to position the United States as an impartial broker in the region.

In so doing, he is dramatically testing the limits of America's clout with Israel.

Israeli leaders such as Begin, Yitzhak Shamir and Ariel Sharon have defied their superpower ally. Netanyahu has something of a mandate to follow suit: His right-leaning coalition took office 10 weeks ago on a wave of voter apprehension that withdrawing Israeli troops and settlers would turn the West Bank into a base for militant rocket attacks, as the 2005 pullout did in Gaza.

Obama has made it clear that he expects Netanyahu to fall in line.

"I believe that Prime Minister Netanyahu will recognize the strategic need to deal with this issue," the president told reporters last week, drawing a parallel with President Nixon's opening to China in the 1970s. Netanyahu "may have an opportunity that a . . . more left leader might not have," Obama said. "It's conceivable [he] can play that same role."

Torn between the demands of a popular U.S. president and those of domestic allies who could turn against him, Netanyahu has scheduled an address Sunday to spell out his policy on the conflict. He is expected to stake out a middle ground, signaling acceptance of previous Israeli agreements to work for a "two-state solution" but insisting on limits to Palestinian sovereignty and avoiding mention of settlements.

Even that vague formula, reported in Israeli news media speculation about the speech, has provoked cries of protest in his staunchly conservative Likud Party.

Palestinian Authority President Mahmoud Abbas' position is also tenuous. The would-be leader of an independent Palestine appears to have no strategy to reassert control over Gaza, which Hamas took by force two years ago, and is so hamstrung by infighting in his own Fatah movement that he's scarcely able to govern the West Bank. His weakness helps explain Netanyahu's reluctance to negotiate with him on the core issues of a peace accord: borders, conflicting claims to Jerusalem and the status of refugees.

Such constraints are familiar to American mediators whose efforts to carve out a permanent accord have persisted over the decades out of a belief that "left to themselves, the Israelis and the Palestinians can make only war, not peace," as Zbigniew Brzezinski, President Carter's national security advisor, once put it.

American pressure sometimes works, but not always as intended. Goaded to limit settlement growth and negotiate with the Palestinians, Sharon rebuffed the George W. Bush administration but withdrew soldiers and settlers unilaterally from Gaza. The move enabled him to win quiet U.S. acquiescence to keep enlarging West Bank settlements.

President Clinton met the limits of his influence when a push late in his presidency fell short of a deal on Palestinian statehood. It invariably takes decisive Arab and Israeli leadership to achieve a breakthrough. Egyptian President Anwar Sadat's bold decision to break from the Soviet orbit, for example, led to Egypt's 1979 peace accord with Israel.

Carter sealed that agreement, showing that American diplomacy works best when adversaries are willing to take risks to end conflicts.

In the absence of such political will, "it's really hard to imagine how you get Abbas and Netanyahu into a negotiation that leads to a conflict-ending agreement," said Miller, who served Republican and Democratic administrations as a negotiator. "Why inflate expectations in such a grandiose manner when the odds of a breakthrough are so low?"

"They'd be in the same situation as always, with Israel strong enough to resist a two-state solution and the Palestinians too weak to force one," said Mouin Rabbani, an independent Palestinian analyst based in Jordan. "I don't see Obama imposing a solution on Israel."

More optimistic analysts believe the administration is in a better position than its predecessors to muster Arab support for a compromise. Obama's conciliatory address to the Muslim world will help, they say, as will Egyptian and Saudi wariness of Iran's growing power in the region.

Mitchell is trying to encourage Syria and other Arab states to start normalizing relations with Israel and is expected to play a far more active role in mediating any Israeli-Palestinian talks than U.S. officials did under President George W. Bush.

"When you realize how quickly Obama has repositioned the United States, you have to say he has a fighting chance of making peace in the Middle East," said Robert A. Pastor, professor of international relations at American University in Washington and an election observer in Lebanon.

"Everybody in the region is waiting for Obama's next move, and it's coming. . . . The United States is going to be right there, listening to all sides, drafting papers, helping to bridge differences."