WASHINGTON (AP) _ Despite the recent buildup of U.S. naval forces in the Mediterranean, Washington has almost no military options to aid the eight Americans held hostage in Lebanon, government officials say.

''There is not a lot we can do to help the hostages,'' one Pentagon source acknowledged privately.

U.S. naval activity off Lebanon tapered off Friday, although two Marine assault groups remained in the area.

One of two aircraft carrier task forces suspended its patrol of the waters off Lebanon, while a three-ship Mediterranean Amphibious Ready Group carrying 1,900 Marines had linked up with a five-ship force carrying a similar number of Marines south of the island of Crete.

During the buildup of the last two weeks, Pentagon and White House officials said they planned no military strike but wanted to be prepared for possible retaliation if the kidnappers began executing hostages.

The fleet might also be used to evacuate several hundred American citizens who remain in Lebanon, Pentagon officials said.

The U.S. military record in the region has been mixed in recent years.

In 1980, an American mission to rescue U.S. hostages in Tehran failed, and three years later, 241 U.S. servicemen died in the bombing of a Marine barracks in Beirut.

The Reagan administration had better luck in 1985, using Navy warplanes to divert an airliner carrying the hijackers of the Achille Lauro cruise ship. And last year, U.S. forces outgunned Libya in air and naval attacks.

The situation in Lebanon does not invite the same kind of intervention practiced by President Eisenhower, who in July 1958 landed Marines to help Lebanese President Camille Chamoun prevail in a civil war.

By 1983, when President Reagan sent Marines to join an international peacekeeping force in Lebanon, civil war had all but destroyed any semblance of government.

Overriding the objections of the Marine commander on the ground, Col. Timothy Geraghty, the White House ordered a naval bombardment of anti- government forces in September 1983, according to Pentagon sources.

The naval bombardment, which claimed some civilian casualties, raised anti- American sentiment in Lebanon. And that hostility was reponsible, in part, for the subsequent bombing of the Marine barracks and the wave of kidnappings.

The exact location of the hostages in Lebanon is not known, according to administration officials, and even a commando raid against a specific site might cause the kidnappers to kill their captives before they could be freed.

A naval bombardment or air strike against Lebanon, similar to those of late 1983, likely would hit civilian targets and serve little purpose other than to deepen local hostility toward Washington, Pentagon officials said.

The U.S. buildup has caused some concern in the Middle East and in Western Europe.

Belgian Foreign Minister Leo Tindemans said he raised the issue in a meeting Friday with Secretary of State George P. Shultz, but did not ask directly about U.S. military plans.

''I thought that for me it (would be) rather undiplomatic to ask that question of Mr. Shultz because he's not responsible for military action,'' said Tindemans.

He noted that some West Europeans nations had tried to talk the United States out of its air raid against Libya last year, and described that attack as ''a source of frustration.''

Pentagon spokesman Robert Sims said the current buildup was meant to show U.S. concern ''about rising tension in the Persian Gulf and Middle East'' as fighting continued in the Iran-Iraq war and Americans remained hostage in Lebanon.

''We want to make sure that we are prepared if our strategic interests are threatened and to show support for our friends in the area,'' Sims said. The possibility of U.S. military action in the area appeared to recede as the carrier Kennedy began a port call in Haifa, Israel, and four of its escorting warships prepared to sail for the United States from Spain.

The Kennedy was left with an escort of five warships, and the other carrier in the area, the Nimitz, was accompanied by 11 ships.