A U.S. military team was in the embattled strategic mountain town of Suq al Gharb today on what was described here as an observation and intelligence-gathering mission and came under shelling while fighting raged there for the 10th day. Its presence appeared to mark one more step in the deepening U.S. involvement in the war here.

Late tonight, U.S. warships again bombarded the heights above Beirut in an effort to stop shelling from Druze-controlled territory that landed close to the American ambassador's residence and hit the grounds of the Lebanese Defense Ministry, both near Baabda.

U.S. Embassy spokesman John Stewart said Ambassador Robert S. Dillon was at the residence when it was "fired upon or rounds came very near" it, but he said the building was not hit and Dillon was not hurt.

Today was the first time U.S. forces have been seen in a battle zone outside their own perimeter at Beirut International Airport and embarrassed Lebanese Army officers prevented American journalists present at the time from speaking to those spotted in Suq al Gharb.

A Marine spokesman, Warrant Officer Charles Rowe, said the team, which included Marine and Army personnel, had gone to the town as "observers" to gather information for Marine commander Col. Timothy J. Geraghty about the overall situation there.

"From time to time, the commanding officer needs observers to give him necessary information and that's their function there," he said.

Asked whether they had been sent to direct U.S. naval and artillery fire on Syrian-backed Druze militia positions around Suq al Gharb, Rowe replied, "Not at this time." But he added, "Their role can change at any time."

The Pentagon said that "over the past several days" U.S. military personnel have gone to the Suq al Gharb area to observe the effects of American naval gunfire. It said, "They are not there to advise the Lebanese Armed Forces."

Yesterday, American warships standing off the coast pounded positions of the Druze and their allies to prevent the fall of Suq al Gharb, situated on the heights overlooking the presidential palace and commanding access routes into the southern outskirts of the capital.

The U.S. government has taken the position that continued Lebanese Army control of the town is of vital interest to the protection of the 1,200 American Marines and the U.S. diplomatic mission here.

There was continued shelling and at least one Druze-led ground assault on Suq al Gharb today while the American military team was visiting. There were no reports of any injuries among the Americans. Small-arms fire was exchanged between Shiite militiamen and the Lebanese Army along the fringes of Marine positions near the airport.

The fighting came amid cautious hopes that Saudi-American mediation to obtain a cease-fire was narrowing differences between the Lebanese government and the Druze and their Syrian backers. One senior Lebanese official said that "the points of difference have been narrowed down to almost insignificant differences." But he added that he feared negotiations might still drag on for another two weeks.

"There is no military solution to the Lebanese crisis," said Foreign Minister Elie Salem, adding that a cease-fire and the start of a political dialogue were imperative.

U.S. special envoy Robert McFarlane and his deputy, Richard Fairbanks, were in Damascus today for talks with Syrian Foreign Minister Abdel Halim Khaddam and later flew to Cyprus to meet with Saudi and Lebanese emissaries to discuss a new Syrian draft of a cease-fire accord.

Considerable mystery surrounded the mission of the U.S. military team sent to Suq al Gharb. It consisted of at least one Army colonel and two marines who were filmed by an ABC television crew getting out of a Lebanese armored personnel carrier and entering the Lebanese Army command post in the besieged town.

Some reporters who witnessed the scene said they saw three American soldiers in the group, while others said there were as many as six. Lebanese Army officers herded the reporters into another personnel carrier when it became clear that the Americans did not want to be seen there.

But reporters were able to see the last name and rank of an Army Col. "Gatanos" who they said was carrying a walkie-talkie while one of the marines was carrying an M16 rifle. In addition to the 1,200 marines in the multinational peace-keeping force, about 80 U.S. Army officers and Special Forces troops are in Lebanon to train the Lebanese Army.

Asked about the Americans' presence in the combat area, Marine spokesman Maj. Robert Jordan said, "It's in our vital interest and the more information we get the better we will feel. The commander felt the need for observation by marines."

Western military sources said the reason for the increasing U.S. involvement at Suq al Gharb was not primarily to protect American lives as the U.S. Embassy has stated. "That was not the major reason," said one military source. "If the Lebanese Army loses that ridge they don't have a negotiating stance."

Meanwhile, a senior Lebanese official said that the main remaining differences in the negotiations for a cease-fire center on the composition of a military team to oversee the cease-fire and a committee of Lebanese leaders to discuss internal political issues.

All sides are reported to have agreed to accept the presence of U.N. observers but Lebanon is still pushing to have a large number of Italian and French soldiers, he said.

On the issue of the composition of a committee for national reconciliation, Lebanon reportedly was still insisting on including Prime Minister Shafiq Wazzan and parliament Speaker Kamal Assad over Syrian objections.

A senior Lebanese official said all sides had tentatively agreed to a cease-fire in place and that Syria and the Druze were no longer demanding Army withdrawl from Suq al Gharb and some other positions in the mountains before halting the fighting.

Meanwhile, state-run Beirut radio said Army soldiers shot five of 15 "infiltrators" attempting to cross from the embattled mountains into the tense Shiite slums in southern Beirut, just north of the airport, yesterday. The Army declared a 24-hour curfew in the area and warned that violators would be shot without warning.

Residents said at least one of those shot today was a tomato picker working in the fields. His foreman implored an American visitor to ask U.S. authorities to end the ban which effectively forbids cultivation at the many greenhouses in the area.