BEIRUT, OCT. 15 -- Before inviting Syrian troops to help oust rebel Gen. Michel Aoun last weekend, Lebanese President Elias Hrawi sought assurances from the United States and, indirectly, from Israel that a Syrian assault involving warplanes and tank and infantry units would not be opposed or obstructed, a Hrawi adviser said today.

"The president sent out feelers to the Americans through the Lebanese ambassador to Washington" and other top Lebanese officials, the source said, adding that the envoys all obtained almost identical guidelines from senior U.S. officials they met in Washington and Damascus.

The U.S. message, according to the Lebanese official, said in effect: "We will not give you a green light, but you are a legitimate government we recognize, and we understand any step you may have to take. If you succeed, we will congratulate you. If the battle is prolonged, we will have to express our regret over the continued violence in Lebanon. If you fail, we will not condemn the action but call on the Lebanese to resort to dialogue to sort out their differences."

Lebanese officials interpreted this response as a clear signal that they could request Syrian military assistance to remove Aoun, who had refused to recognize Hrawi as the country's president, without fear of U.S. disapproval.

"The nuance was subtle," Hrawi's adviser said. "We were told to decide on our own, and it was really between us and the Syrian government. But until the last minute we waited for assurances from the Americans on how Israel would react and the answer was: Israel will not interfere as long as Syria does not approach south Lebanon or threaten {Israel's} security interests."

The source said that among the contacts was a meeting in Damascus a month ago between Lebanese Prime Minister Selim Hoss and Edward Djerejian, the U.S. ambassador to Syria.

In Washington, State Department spokesman Margaret Tutwiler today denied that the United States gave Syria "a green light" to move against Aoun. Asked if it had given Syria a red light, she said: "We did not give them any lights."

One U.S. official familiar with the messages that had been passed said "there were a lot of rumblings" of possible Syrian participation for two weeks before Aoun's ouster, and in response the United States communicated to both Lebanon and Syria that it would not approve of an armed offensive against Aoun.

But commenting Saturday on Aoun's removal after it happened, the State Department said: "We hope this ends a sad chapter of Lebanon's history and that the Lebanese people can now move toward reconciliation and the rebirth of a united, sovereign and independent Lebanon."

Officials close to Hrawi provided new details about Aoun's final hours at the presidential palace in Baabda, which he moved into in 1988 as head of an interim military government and refused to relinquish when the parliament elected a new president last year after long negotiations in Taif, Saudi Arabia.

The sources said an attempt had been made to persuade Aoun to hand over the palace to Hrawi's army commander, Gen. Emile Lahoud, 15 minutes before the Syrian jets arrived to bomb his bunker. Aoun rebuffed this request, but surrendered less than an hour later, the Hrawi aides said.

Col. Ghazi Kanaan, Syria's chief of military intelligence in Lebanon, told Hrawi that Aoun contacted him on Thursday, the day Lebanon officially requested Syrian assistance to put an end to Aoun's rebellion. Aoun sought to make a deal with Syria and made an appointment to send an envoy to meet Kanaan in the Syrian-controlled Bekaa Valley.

"I set an appointment for Saturday, 10:30 a.m., knowing it would all be over by then," Kanaan told aides of Hrawi.

In an interview today in West Beirut, Hrawi said: "I tried everything. The man would not budge. I offered him government posts and asked him to work with us. We wanted to spare him and avoid getting the Syrians into east Beirut."

France opposed the Syrian-backed attack, according to the Hrawi advisers. Aoun, whom the Hrawi government wants to put on trial, finally took sanctuary at the French Embassy.

French President Francois Mitterrand pledged in Paris today that France will continue to give refuge to Aoun until Lebanese authorities allow him to leave Lebanon for France, where he has been granted political asylum. Mitterrand called it "a question of honor for France."

Unconfirmed reports of looting and rape in Christian areas overrun by Syrian soldiers and their local allies brought an angry reaction from Christian Phalange Party head George Saadeh, a legislator who endorsed the Arab-sponsored Taif accords last year. "We did not eliminate one state of rebellion to have a new one," he said urging the government to put an end to the chaos.

Over lunch with visitors, Hrawi said later: "All these people who have been clapping for Aoun all these months are complaining now. My main task is to restructure the Lebanese army and abolish the religious barriers on which the army's brigades were formed."

"The reason I asked the Syrians to help is because I had no arms, no materiel, no tanks, no guns, no boots, no combat fatigues and no walkie-talkies," he said, describing his woefully under-equipped army of 10,000 now being carefully merged, under Syrian monitoring, with Aoun's forces, estimated at 15,000.