Beirut — The twisted remains of cement and wires lying by the Beirut airport are an unofficial memorial to the 241 US marines killed one year ago Tuesday by a terrorist.
The concrete skeleton also symbolizes the remaining American presence in Lebanon which has been effectively ''bombed out'' of the little nation both physically and diplomatically. That presence is about to shrink even further with the Reagan administration's decision Saturday to greatly reduce the number of staff members at the United States Embassy.
The embassy staff had already been reduced from 99 to 45 after last month's bombing of the embassy annex in east Beirut, according to the US State Department, and could be cut to about 30 by the latest move.
The few American diplomats remaining in east Beirut live in virtual fortresses, their movements restricted to daylight; most areas of the capital are off-limits. Having lost two embassy buildings in 17 months, they are working out of Ambassador Reginald Bartholomew's residence, their own apartments, and the back of the bombed-out annex, now tightly guarded.
The new embassy in west Beirut, opened in August, is empty. The Muslim-dominated half of the capital is considered too dangerous for an American presence. Shiite Muslim extremists are held responsible for the three attacks on American targets.
One year ago, the US presence was at its height: US special envoy Robert McFarlane was the chief peace negotiator. The Marines had just marked their first year in the multinational peacekeeping force in Lebanon. More than a dozen warships - including one of the world's two battleships, the USS New Jersey - were anchored offshore.
Many Lebanese felt the Americans were running their country.
Today, the US is almost totally out of the picture: The peace effort is now being orchestrated by Syria. The marines abandoned their bunkers eight months ago.
Lebanese and Western sources report that recent hard intelligence supports the fears of another imminent bombing, perhaps with explosives left over from the annex attack.
According to reports, an attack has been threatened to occur before the US elections Nov. 6.
Shortly after the Sept. 20 blast, Islamic Jihad - the shadowy group that claimed responsibility for all the anti-US violence - pledged it would strike again soon.
A new threat of kidnappings has also heightened alarm - and security. On Friday, the State Department said that all the remaining American dependents in Beirut were being evacuated. Three Americans - a diplomat, a journalist, and a missionary - kidnapped last spring are still missing.
The embassy, just one year ago the busiest and largest in Lebanon, refuses to release information about its activities, the threats, or how many diplomats are here. Information must be gleaned from other Western envoys.
Yet as of Friday there were still an estimated 5,000 American citizens in Lebanon, 1,500 of which are living in Beirut. While the vast majority are Lebanese Americans, there is a nucleus of native-born Americans who have been in residence anywhere from one to 30 years.
And many of them are not surprised by the anti-American atmosphere - nor overly alarmed by the threats.
Carol Weir's husband was one of those kidnapped, missing since he was grabbed off the street in front of their home by unidentified gunmen as they were out for a walk last May. Ben Weir, a Presbyterian minister, had lived in Lebanon since 1954.
''I don't think my husband's kidnapping was a personal act against him. He's been kept because of our policy. It's a protest against our foreign policy,'' Mrs. Weir said last week.
The kidnappings and bombings, notes a source close to the Weir family, ''provide more evidence that the US has been unable to maintain an even-handedness in Arab-Israeli matters. The US is losing its credibility as a mediator in the Arab world.
''The violence which occurs is produced by the US's inability to look behind the causes of violence and to deal with those causes,'' the source adds. ''I also see an increased anti-American climate, which makes this kind of violence possible.''
Last February, Frank Regier, an engineering professor at American University of Beirut (AUB), was one of the first Americans to be kidnapped. He was held 66 days by still unidentified gunmen until he was rescued by the Amal Shiite militia. He is now on sabbatical at Yale University, but his wife remains at AUB where she is a math professor.
''I am sure it wasn't personal,'' she says. ''I think (this is) what happened: The Americans were being evacuated that day, which reflects on the local people. Perhaps it means (to them) 'we don't trust you.' This happened two or three days after the big New Jersey shelling. Here is a tall, fair-haired, obvious American on the street. Perhaps that made someone mad.''
Placing ultimate blame on US foreign policy and actions on the ground for the bombings and kidnappings was the single common theme among American businessmen, professors, relief workers, and housewives still in Lebanon. Each said in effect: In light of its attitude and policy, the US should expect a negative, and even violent, reaction.
The American wife of a professor at Beirut University College was evacuated briefly during last February's fighting, when US Sixth Fleet warships often opened fire. She says she had wanted to have a T-shirt made which declared: ''America made me get out of Lebanon,'' a reference to her fear that there would be reprisals against Americans because of US military intervention.
Neff Walker has just begun his second year as a psychology professor at American University. ''I was not surprised when the annex blew up. One could assume that once (the US) vetoed the UN resolution (critical of Israel's two year occupation of south Lebanon), something was going to happen.'' The veto is widely considered to have been the motive for the annex blast.
Nor do the Americans interviewed feel the violence is over. ''There are going to be more explosions, I'm sure,'' says a Beirut University College professor, just one of the many Americans who did not want to be named.
Most Americans are trying to keep a low profile. Although embassy figures from a year ago indicate roughly 1,000 American citizens have left Lebanon over the past year, many are determined to stay.
George Mead is the last American banker in Beirut. Despite some near misses when he has been caught in fighting zones and three recent personal threats, he plans to stay ''indefinitely.''
''It's not just my career. It's stimulating and educational. And it's not the case of someone who needs to live on an edge to get a thrill.'' But like many Americans, he varies his schedule, traveling at irregular times between east and west Beirut, limiting the places to which he goes socially.
''I don't feel endangered by any known organization. I'm worried about splinter groups, the four- to 10-men groups that operate independently,'' Mr. Mead explains.
Although the anti-US trend has been associated with Muslims, the three threats to him have been from Christian gunmen, and all were related to job disputes. ''I've never been threatened or hassled by the Muslims.''
Catherine Bashshur is principal of the American Community School, which is down to an all-time low of 66 students from a high of almost 1,000 before the civil war broke out in 1975. Only 15 of the students are American.
Islamic Jihad's latest threat specified that all American institutions were targets. But Mrs. Bashshur, who has lived here for 20 years, was more worried when US diplomats were temporarily located next to her school than she is now. Security, she says, was inadequate.
''Any crazy could have come via our playground to blow up the back of the British Embassy,'' where the US set up offices after the April 1983 embassy blast until the move to east Beirut this August.
Professor Walker, who is doing research on the impact of stress after almost one decade of war in Lebanon, says he has not noticed any by-products of stress among the Americans he knows.
The one thing that does worry him, however, is the fact that every time he is stopped at a road block he is asked in Arabic if he is safara.
''That means embassy,'' he explains.
''Everyone wants to know if I am with the embassy. I keep telling them 'no, no, no.' Why do they want to know if I'm with the embassy, I ask myself. That does make me nervous.''