Buenos Aires — Argentina is prepared to seek Soviet military assistance if the United States continues to support Britain in the Falklands crisis.
This warning - said to have been issued by an unidentified member of Argentina's ruling three-man junta - appeared May 24 in the pro-government newspaper La Nacion. It appears to be the first officially inspired leak on the issue to appear in print here.
Foreign Ministry sources have confirmed the warning and suggested it was a psychological move aimed principally at the US. Argentina wants the US to adopt a more neutral line in the conflict and to force Prime Minister Margaret Thatcher to the negotiating table. Defense Minister Amadeo Frugoli said Monday that the US as the leader of the Western world should assume its ''responsibility'' and try to defuse to conflict.
Buenos Aires believes that the Reagan administration is deeply concerned about the possibility of the Falklands crisis becoming internationalized and about US influence in Latin America perhaps being undermined to the advantage of Moscow.
At the same time, the junta sees an end of US support for Britain as a necessary first step toward repairing US-Argentine relations - relations that were severely damaged following the breakdown of US Secretary of State Alexander M. Haig Jr.'s mediation effort. This view is believed to have been put across during the recent visit to Buenos Aires of Gen. Vernon Walters, one of President Reagan's trouble-shooters.
Publicly, Argentine-US relations have hit their lowest point since President Leopoldo Fortunato Galtieri took power in December. Washington is criticized by the junta for having ''betrayed'' the strong relationship developed in recent months as a result of Buenos Aires's willingness to support Reagan policy in Central America.
Reluctantly, Buenos Aires now acknowledges that the United Nations peace effort has had very little influence on Mrs. Thatcher, and that Washington remains an essential ingredient for any serious breakthrough on the diplomatic front.
According to diplomatic sources here, the ''Argentine-Soviet card is a genuine reflection of the view of some military officers'' who are prepared to hang on to the Falklands at all costs, rather than risk the political humiliation of military defeat.
The Argentine news media Monday continued to claim that Argentine armed forces were ''in control'' and had completely surrounded British forces near San Carlos, after the British were attacked by the Argentine Air Force Sunday.
But military sources here are admitting for the first time that their disposal to seek outside military assistance stems from a fast-depleting supply of equipment and difficulties in securing additional supplies because of the British blockade.
(Although Argentine official estimates of losses are low, Britain claims Argentina has lost at least 30 combat warplanes.)
''We have thrown a lot at the British, but there's going to come a point when we're going to be left without military equipment unless we accept the offer of outside help from whatever source,'' a military source said.
(A South African newspaper, the Johannesburg Star, reported Monday that South Africa has agreed to sell to Argentina spare parts for Mirage jets and surface-to-surface missiles.)
Independent observers here say official Argentine military communiques have continued to seriously understate the damage wrought on Argentina's troops and Air Force since serious fighting broke out.
Politically, however, the question of Soviet military assistance is highly controversial and continues to deeply divide the Argentine armed forces. On the one hand there are the hard-line nationalists who are prepared to stake anything to secure a perceptible victory over the British.
On the other, there are military officers who, because of their background, training, and politics, retain strong links with the US and may be reluctant to call on Moscow.
Many Argentine officers and virulently anti-Marxist and believe the Soviet Union is behind left-wing subversion in Latin America.
Ironically, it was precisely this assessment of the world balance of forces that led President Galtieri to offer Argentina's support for the Reagan administration in Central America. However, since the Falklands crisis broke out , El Salvador appears to have been moved down on the list of priorities.
Until now the Argentine military junta has adopted a pragmatist attitude in its trade relations with the Soviet Union. It refused to support the Carter grain embargo toward the Soviets and allowed Moscow to become Argentina's main cereal purchaser.
It remains to be seen whether pragmatism and Soviet interest in the area will be sufficient to jolt some Argentine military officers out of their ideological convictions. Military sources here suggest that a compromise between the two could be acceptance by Argentina of military aid from third parties such as Libya.