Late last year, as trouble in Poland was growing, a U.S. State Department official called a high Argentine diplomat into a "briefing" on the tension. As an Argentine source described the meeting later, it was an obvious effort to ensure that Argentina would join any actions against the Soviet Union -- that it would side, as the American reportedly put it, with "the allies."

At that the Argentine was forced to interrupt. Argentina, he said, does not consider itself part of any alliance. Argentina, by longstanding tradition, is "neutral."

Thus an official of one of the world's most fervently anticommunist nations politely refused to enlist against the Soviets, and the reason was obvious. Argentina -- where government-line magazines link Marxism with the antichrist and leftists have been purged with a vengeance that appalled international human rights organizations -- sells more of its grain and meat to the Soviet Union than any other country.

Of 1980's grain crop, by far the country's most important export, 60 percent -- 7.5 million tons, according to local newspapers -- was sold to the Soviets. That is an enormous increase over 1979, because when the United States protested the 1979 Soviet intervention in Afghanistan by declaring a boycott on grain sales to the Soviets,; the Argentines ignored the boycott and surged ahead with their already healthy Soviet trade.

Breaking the boycott was partly a satisfying swipe at the United States, which during the Carter administration infuriated officials here by singling out Argentina as one of the Western Hemisphere's most repressive governments. But it is highly unlikely that even in friendlier times Argentina would have spurned all those rubles.

Under the label of "neutrality," the Argentines have fashioned a wondrously flexible foreign policy that has only two consuming goals: fending off neighboring Brazil and Chile and selling Argentine products. The rest has consisted over the years of equal parts pragmatic nationalism, independence from the United States and something that an irritated Buenos Aires journalist once described as "bobbing up and down the international line-up in a highly disconcerting fashion."

This is the country that refused to break relations with Germany and Japan during World War II, then presented the United States with a request for military aid -- denied -- and finally declared war on the Axis two months before the war ended.

Although its military government rings with political rhetoric about defending "Western, Christian values," Argentina belongs to the nonaligned nations. At the recent nonalaigned conference in New Delhi, Argentine delegates startled observers here by joining a subcommittee that included Tanzania, Nigeria and the Palestine Liberation Organization. In exchange for nonaligned support on issues such as human rights and the British occupation of a group of Atlantic islands still claimed by Argentina, Argentina frequently votes in favor of sanctions against Israel -- and Israel, by many reports, supplies Argentine with arms.

Three months before Buenos Aires hosted the 1980 congress of the Latin American Anticommunist Federation, where one delegate was quoted as declaring, "The only good comunist is a dead communist," Argentine President Gen. Jorge Videla became the first Latin American head of state to visit the People's Republic of China.

The Argentines were cordially received, signed broad agreements for future cooperation in agriculture and natural resources and spoke glowingly upon their return of the time when Argentina would eventually export industrial plants to China and join the People's Republic in large work projects. The Argentines reportedly even offered to send two soccer coaches to visit China for three-month teaching sessions in the Argentine national sport.

Addressing these warm relations with China and the Soviet Union gives Argentine diplomats pause, but not a very long one.

"The enemy we had before us in our fight against the revolutionary left was an enemy that came from Cuba, not from Russia," said an Argentine Foreign Ministry source. "Besides, we have a fundamental problem, especially when we are politically isolated from the rest of the world. We have to eat. It is not an ideological question, but a question of survival."

President Reagan's Latin American advisers have spoken frequently about the deterioration of U.S.-Argentine relations during the Carter administration, worrying, as one adviser wrote in a recently published article, that the United States has "lost" Argentina to the Soviets. Almost without exception, they blame former president Jimmy Carter's human rights policy for that. The State Department under Carter became a steady public critic of arbitrary arrests and kidnaping by Argentine security forces and in 1978, reacting to those and other criticisms, Congress cut off all arms sales to Argentina.

By the end of Carter's presidency, the government-line Argentine press had made a national bete noire out of Patt Derian, Carter's assistant secretary of state for human rights, and Argentine officials were enormously pleased about the election of an administration that clearly intended to play down human rights as a foreign policy priority. Many people assume here that under the Reagan administration, the United States will eventually resume military and possibly nuclear equipment sales to Argentina.

But the Argentines show no signs of willingness to shut out the Soviets as part of a warmer U.S-Argentine relationship. It would be practically un-Argentine for them to do so.

"Historically, Argentina has been one of the prime movers in attempting to restrict U.S. influence and maintain its own international options," said a Western diplomat here. "This goes back to the last century."

U.S.-Argentine relations lurched into being in the early 1800s, when Argentina was declaring its independence from Spain. One of the early Buenos Aires envoys, an Argentine dispatched to North America to see about buying arms, was thrown into a New York jail and accused of high treason.

Five years later, the first U.S. minister arrived in Buenos Aires. After being forced to suspend his credentials ceremony because of a fierce attack of apoplexy, in his seventh month of service he attended an Argentine party, became violently ill afterward and died.

At intervals, especially after North American protective tariffs hurt Argentine wool exporters in 1980, it has been touch and go. Argentina has traditionally resisted U.S.-sponsored efforts at hemispheric alliances. When Woodrow Wilson proposed a hemispheric peace pact during the years before World War I, Argentina countered by suggesting multilateral Latin American agreements that would leave out the United States.

Like much of Latin America, Argentina remained neutral during World War I. In World War II, Argentina was the last Latin American country to enter the war -- and then did so, according to most versions of the story, so that the country would be admitted to the fledgling United Nations.

"Argentina had developed a nationalistic sector that was very friendly toward Germany, and this sector influenced the government to help Germany," said retired Argentine Admiral Isaac Rojas. "[Juan] Peron, of course, was an admirer of Nazism and fascism, and he declared war against Germany when they were defeated, which made us look ridiculous before the whole world."

Peron established relations with the Soviet Union in 1946, after more than 20 years of rupture. As part of his much-publicized "third position," which Peron described as an alternative to individualism or collectivism, Argentina tried to maintain distance from the cold war.