A tight little knot of ''diplomats'' confers heatedly outside a ''United Nations'' committee chamber.
Suddenly the caucusing erupts into laughter as a member of an Arab delegation , wearing the traditional headdress and a ''Blue Oyster Cult'' rock 'n' roll T-shirt, claps his hand over his face in disbelief.
''But,'' he moans in response to a Chinese delegate's proposal, ''China would never do that.''
The Communist Chinese representative, seeing the pro-capitalist tilt of his position, takes the unsolicited advice with a sheepish grin and readjusts his approach to the issue at hand. Thus, the balance is reset and the negotiating continues - no hard feelings, no international imbroglio.
The importance of diplomatic subtlety, though, is not lost on these ''UN delegates'' - actually high school student participants in the annual Harvard University Model United Nations conference. Role-playing a four-day slice of UN business - including an overnight session to handle a hypothetical crisis between Libya and Egypt - 1,400 North American teen-agers maneuvered through the labyrinth of parliamentary minutiae and international issues trying to reach solutions to world problems. And fresh from this year's Falkland Islands war, the Israeli invasion of Lebanon, continued martial law in Poland, and scuttles between South Africa and its neighboring countries, there was plenty to deal with.
Although there were no Nobel Prize-winning results to come out of the recent conference, the initiation of ideological youth to the facts of life smoothed the rough edges off future Henry Kissingers and Alexander Haigs (maybe even a few future Jeane Kirkpatricks, although there appeared to be a 10-to-1 boy-girl ratio at the conference, and the few girls attending often took a conspicuous back seat to the boys).
Faculty advisers at the conference say that more important than reaching solutions to problems, students are given a chance to learn the gentle - and not so gentle - aspects of persuasion and compromise, oratory and debate, the fundamentals of politics, and awareness of the world as a whole.
Robert Nuxoll, a faculty adviser from Oceanside High School in New York, says he always asks that his school represent a third-world country at the model UN - this year it was Togo. He explains that his students come from Nassau County, with one of the highest average annual incomes in the United States. The contrast these students feel between their own lives and the concerns they must argue on behalf of third-world countries, he says, is the most important learning experience of the conference.
Even if students aren't always aware of what they're learning, says James Shelland, a faculty adviser from Great Neck North High School, in Great Neck, N.Y., ''they get a kick out of saying exactly the opposite of what they really believe in . . . like giving the Soviet line on Israel. They may even take a better position in being the devil's advocate, perhaps because they can anticipate what the opposition will be.''
There is rarely unanimous approval of any issue before the UN, explains Brenda Buttner, a Harvard senior who helped run the model UN. An idealistic teen-ager who comes to the conference usually has a ''glamorized'' image of diplomacy and ''is divorced from the reality of international problems,'' she explains.
While some of their wide-ranging, if well-intentioned, resolutions for world peace were unsuccessful, students still were able to take home new ideas.
''People sometimes say the UN is failing. . . . I can see now why they say it ,'' explained Liz Frazier, a junior from Southbury, Conn., whose high school represented the Polish delegation to the UN. ''But I learned there are so many angles from which you can view an issue [that total agreement on any settlement is unlikely] and that other things, like compromise, are important.''
Kevin Green, a Deerfield, Ill., senior representing East Germany, said he enjoyed it most when he could get others to compromise. Exercising his new-found persuasive ability, he was able to get an Irish delegate to side with the communists in their support of Libya in a dispute with Egypt - something the young delegate admits would not happen in reality.