Moscow — The Mexicans, Brazilians, and Argentines may not be in the same ideological trench as the Kremlin, but they are figuring more and more importantly in Soviet policy toward Latin America.
Pesos, rubles, and Brazilian cruzeiros -- that is, trade -- seem to count as much as idealogy in the Sovieths realigned approach south of the United States border.
Argentina has been helping the Soviets counter shortfalls in grain and mead supply that were due in part, Western experts argue, from the recently lifted US grain embargo.
Senior trade delegations from Brazil and Mexico are due for talsk in Moscow in the coming weeks.
The Soviets are openly cultivating closer economic ties with the major noncommunist states of Latin America.
Foreign diplomats here suggest a number of explanations for this. First, notwithstanding public cheerleading for "popular" forces in Latin America, the Soviets are seen as neither seeking nor expecting any major, short-term clash with the United States in an area so close to its shores.
On the pattern of detente with Western Europe, long- term Soviet interests will theoretically benefit from widened links with emerging regional powers in Latin America -- particularly the Mexicans, buoyed by oil discoveries, and the Brazilians.
Finally, the diplomats note, such a move makes good sense in purely economic terms, particularly in the case of the Argentines.
This last point can't be applied to Soviet relations with a state like Cuba, a longtime ideological ally whose economic needs have drained billions of dollars from Soviet state coffers in the past two decades.
Although by no means abandoning the Cubans, Moscow publicly distanced itself from Fidel Castro's alleged backing of Salvadorean rebels when President Ronald Reagan made an issue of this earlier in the year.
And when representatives of Nicaragua's revolutionary regime came to Moscow last year to economic talks, diplomats here say, they went home virtually empty-handed.
In his lengthy policy report to the Soviet Communist Party congress in February, Soviet President Leonid Brezhnev made only passing reference to Cuba and Nicaragua -- and none at all to unstable El Salvador.
But he said: "The role in world affairs of Latin American countries, such as Mexico, Brazil, Argentina . . . has grown."
So, he said, had Soviet relations with these states, and he hoped the trend would continue. He included Peru and Venezuela, another oil producer, in this category.
The Soviets' official 1980 trade figures show that Argentina was the main beneficiary of what appears to be a move toward depoliticization of Soviet Latin America strategy.
Its total turnover with the USSR leaped from some 313 million rubles to more than 1 billion rubles. In recent weeks, the Soviets have sealed a fresh agreement for grain from Argentina and signed a five-year accord for the import of Argentinian beef.
Trade with Mexico nearly tripled in 1980. But it still stood at only 13.3 million rubles, or about $19 million US at the current official exchange rate.
The Soviets would like to see trade with Mexico expand, and have told diplomats here that Moscow could help the Mexicans develop their bourgeoning oil industry.
earlier in May, Mexico's foreign minister visited Moscow.
Absent from the final communique was the kind of broadside on US policy in Latin America common in the official Soviet press. This did not surprise diplomats, since the Mexican President is slated to meet Mr. Reagan for summit talks soon.
But the statement did say that both sides had the "political will" to expand trade and noted that a senior Mexican economic delegation would be visiting Moscow. The group is expected early in June.
About a month later, a senior Brazilian trade team will be in Moscow, amid indications that various new commercial accords may be signed. Diplomats say these could include expanded Soviet purchases of Brazilian soy -- consistent with Moscow's bid to dent both wheat and meat problems by feeding animals less wheat and more protein-rich commodities like soy.
Diplomats say accord is also likely on sizable Soviet oil exports to Brazil, a past importer of Iraqi crude hurt by the outbreak of the Iraq-Iran war. This would involve what amounts to a swap -- with the Soviets supplying crude to a West European country that imports Middle Eastern oil, while the Mideast nation ships an equivalent amount to Brazil. This would dodge difficulties in shiping Soviet oil to Brazil.
Also reportedly possible during the Soviet-Brazilian talks is expansion of Soviet input into B razil's program to develop synthetic fuel from wood.