Argentina vitually closed the door today to cooperating with the U.S. effort to hold down grain sales to the Soviets, although it hinted that attitude could change if the Carter administration offered political concessions.

Argentina is an important exporter to the Soviet Union of the agricultural products that President Carter is attempting to cut back in retaliation for the invasion of Afghanistan.

Experts here believe Argentina could offset a substantial portion of the 17 million tons of grain, mostly corn and soybeans, that the United States has denied the Soviets.

"We refuse to take part in punitive decisions or attitudes which were adopted without our prior participation or which are taken in centers of decision outside our country," a Foreign Ministry statement said. "A feature of Argentian foreign policy is not to use economic sanctions as a way to pressure or punish. . . ."

Argentina will, nonetheless, send a low-level of delegation to Saturday's conference in Washington, aimed at convincing grain exporters not to increase their shipments to the Soviet Union to make up the 17 million tons.

The Foreign Ministry statement was viewed as almost entirely negative in terms of what, the United States had hoped from Argentina, which has been heavily criticized by the Carter administration for violations of human rights.

But the statement's last paragraph said Argentina would not agree to "unilateral measures not sacrifice, without plainly justified reasons, the legitimate national interests in the context of our peaceful relations with all nations."

Possible "reasons" that might justify cooperation with the United States were outlined in La Opinion, a newspaper published by the Argentina Army.

According to La Opinion, Argentina wants U.S. help in toning down an Inter-American Human Rights Commission report expected to be highly critical of the government here, normalization of military cooperation and support for Argentina's claim to the British Falkland Islands.

The rights commission is an autonomous body carefully designed to be immune to any government's influence. Further, it was understood here that the Carter administration in unlikely to engage in such political trade-offs in return for Argentina restraint on grain sales.

The Soviet Union has better trade and political relations with the right-wing junta here than does the United States, although the junta frequently proclaims its "Western values" and denounces communism.