UNITED NATIONS —France yesterday threatened to go it alone if differences with America on a resolution to end the fighting in Lebanon are not bridged. Playing his toughest diplomatic card yet, President Chirac said his country might end its coalition with America and present its own resolution.

A day after negotiations reached an impasse, however, American officials played down the possibility of two competing approaches to Middle East diplomacy, one led by Washington and the other by Paris. Instead, American officials stressed diplomats’ attempts to resolve the differences.

After the French-American talks deadlocked late Tuesday, Paris fired the first verbal salvo yesterday morning.

“If we don’t manage it, there will obviously be a debate in the Security Council, and everyone will present their position clearly, including of course France with its own resolution,” Mr. Chirac told reporters after emerging from a meeting with members of his Cabinet in southern France.

The American ambassador to the United Nations, John Bolton, acknowledged that negotiations were difficult, but said they might yet yield results. “We reached an agreement with France and other countries last Saturday, and introduced a joint text, contrary to expectations,” Mr. Bolton told U.N. reporters. “We may yet do it again.”

Fresh from a meeting at Turtle Bay with French and American diplomats, the secretary-general of the Arab League, Amre Moussa, quipped, “The gap is wide but not unbridgeable.”

Mr. Moussa, a veteran pan-Arab Cairo-based diplomat, emerged yesterday as the top negotiator for the Lebanese cause, highlighting the weakness of Prime Minister Siniora of Lebanon.

“We coordinate with the Lebanese government,” Mr. Moussa told The New York Sun, “but we support their decision.” Specifically, he referred to a plan Mr. Siniora laid out last week that was reintroduced for American eyes in a Washington Post opinion piece yesterday.

The seven-point plan, which starts with a prisoner exchange and an Israeli withdrawal from Lebanese soil, looked even less realistic yesterday than when it was first proposed as Israel began a major ground invasion to take over the area between the international border and the Litani River, a major launching pad for Hezbollah’s cross-border missiles.

The Israeli ambassador to the United Nations, Dan Gillerman, dismissed what he called “pathetic” attempts by the Arab League to represent “poor Lebanon” at the United Nations.

“If Siniora had agreed to the two points of the U.N. — deployment of his troops in Lebanon and the disarming of Hezbollah — he wouldn’t need seven points, or three points, or five points,” Mr. Gillerman said, referring to several Security Council resolutions that stressed the need for Lebanon to take control over the country’s southern region near Israel’s border from Hezbollah. Mr. Siniora “did not do it, and we now pay a heavy price,” Mr. Gillerman said.

Earlier this week, Beirut announced it was ready to deploy 15,000 troops in the south. The announcement set off a diplomatic scramble to incorporate the new element into the French-American text. Mr. Moussa and the Lebanese diplomats involved in the talks argued that with the help of a U.N. force, the Lebanese army would now enter the Hezbollah-controlled area — but that the Israel Defense Force troops must leave first, and immediately.

Diplomats involved in the negotiations said Paris agreed to the idea of a transfer of the area to U.N. troops and the Lebanese army. But even after the Beirut announcement, American officials repeated their assertion that no “vacuum” should be allowed to remain in the south that might allow Hezbollah to regroup and rearm.

Mr. Bolton said it was clear the Lebanese army’s readiness to enter the south would have to be taken into account. But he also acknowledged that it had complicated the attempts to reach an agreement on a resolution, describing the negotiations as a “moving target.”

A U.N. diplomat involved with Arab and Lebanese affairs told the Sun after he was promised anonymity that Mr. Siniora has been weakened by the war and is unable to grasp the quick changing political realities. “He is overwhelmed by this,” the diplomat said, adding that Paris and, to a lesser degree, Washington are now attemping to prop up Mr. Siniora.

While stressing that he did not dismiss the “interesting” decision to deploy Lebanon’s army, Mr. Gillerman also said he was skeptical of Mr. Siniora’s prowess. “He did not do it in the last six years since we left Lebanon, he did not do it when he had the power and authority,” Mr. Gillerman said. “To expect he would do it now, when he doesn’t have the power, the authority, or the ability, is naïve and an overreach. It looks to me like a maneuver that should not be taken too seriously.”