The U.S. Embassy in Lebanon, already scaled down because of growing anti-American threats, was reduced to a near-skeleton staff today with the evacuation of 18 more Americans.

The evacuation, which was carried out with strict secrecy here, came amid a growing political crisis in the Lebanese government, as a standoff continued between President Amin Gemayel and leaders of the Lebanese Forces, the powerful Christian militia, over the issue of Syrian involvement in Lebanon.

Syria, showing signs of concern at the crisis, sent its key troubleshooter, Gen. Mohammed Kholi, the former chief of intelligence with Syrian forces in Lebanon, to talk with Lebanese officials today.

Embassy officials here refused to confirm reports from Washington that an evacuation was under way, but immigration officials in Cyprus said 18 Americans had been flown there by U.S. Navy helicopters.

Officials in Washington said the "temporary movement" was intended to safeguard nonessential staffers while maintaining enough of a presence to underscore U.S. determination not to be driven out of Lebanon. Details on Page A24.

Three American warships -- the aircraft carrier Eisenhower and two guided missile ships -- are off the Lebanese coast, but it was not known whether they took part in the evacuation.

There was no indication here or in Washington how many American diplomats remain in Lebanon, although most estimates were that there are about a dozen, including Ambassador Reginald Bartholomew, and a similar number of security forces.

Mounting threats have been made against the United States by militant Shiite Moslem groups here, especially since the U.S. veto in the U.N. Security Council on Tuesday of a Lebanese-drafted resolution that would have condemned Israel's actions in southern Lebanon.

The chaos within the Lebanese Christian community has added to the sense of urgency because the only U.S. diplomatic offices still in use in Lebanon are in Christian-controlled territories.

As a result of bomb attacks against the previous U.S. embassy building and an annex, that killed at least 77 persons, and deteriorating conditions in west Beirut, where a new embassy was opened last year, American diplomats have been working mostly out of the ambassador's residence in Yarze, a Christian town a few miles east of Beirut.

A U.S. official reached at Bartholomew's residence told The Associated Press: "We are here, and the embassy continues to function normally. We are continuing to confer with a wide range of Lebanese government officials on the matter."

[United Press International attempted to reach embassy spokesman Robert Gould but was told by his housekeeper he had gone to Cyprus for a three-week vacation.]

While no bloodshed was reported in the dispute between Gemayel, who heads the Christian Phalangist Party, and rebel Christian militiamen opposed to growing Syrian influence in Lebanese affairs, the tense political deadlock continued.

Gunmen from both groups faced other on the barricaded Beirut-Jounieh coastal road amid reported threats by the rebel forces to "take measures" to open the highway by force if necessary.

Although few observers here expect either side to resort to combat, the rebel Lebanese Forces, with more than 6,000 militiamen and fleets of Israeli tanks and other armored vehicles, are considered to be far stronger than the police force controlled by the Phalangists -- and possibly a match for the Lebanese Army, which is made up of Christians and Moslems.

Despite a meeting among breakaway Lebanese Forces commander Samir Geagea and his top aides and mediators seeking a compromise with the mainstream Phalange Party, the rebel leaders hardened their demands that Gemayel end Syria's power broker role in Lebanon and restore Christian decision-making in the government.

Geagea, who controls the Lebanese Forces' artillery and mechanized units and who claims the allegiance of 90 percent of the 6,000 men, tonight demanded a reversal of Gemeyal's attempts at rapprochement with Syria and a revival of Christian "cultural and ethnic identity" in Lebanon.

The Christian heartland was paralyzed today, with militiamen loyal to Geagea in control of the central mountainous areas north of the Nahr Kalb bridge on the road to Jounieh. Schools remained closed in the area, and traffic was abnormally light in usually congested areas of Christian east Beirut.

On the bridge, Phalange Party gunmen loyal to Gemayel manned barricades.

Just to the north, gunmen of Geagea's faction were massing with heavy guns and armored vehicles. The Phalange radio quoted "security sources" as saying the rebels had demanded that the road be opened or the militiamen would take "measures" to open it.

Most of of the Lebanese Forces were reported supporting the hardline and pro-Israeli movement led by Geagea, whose stated goal is to end Syrian hegemony over Lebanon while blocking concessions aimed at reconciliation between the feuding sectarian factions in Lebanon.

In an apparent attempt to strengthen his backing against Gemayel, Geagea met today with leaders of the Christian militia, including the Lebanese Forces intelligence chief, Elie Hobeika, who has been closely allied to Israel.

A senior Lebanese Forces official who would not let his name be used said tonight that "everyone agrees that the government has gone too far with Syria's ambitions in the region." He also said Geagea's followers were upset at Gemayel's public support of the Shiite guerrillas who have attacked Israeli occupation forces.