Secretary of State Alexander M. Haig Jr. said today that a U.S. grain embargo to protest Soviet intervention in Poland "would be self-defeating and sterile" in the absence of support from other western grain-producing nations.

A unilateral U.S. embargo "would not influence or affect the Soviet Union one bit," Haig said after a 2 1/2-hour meeting with the AFL-CIO Executive Council.

Haig's remarks were prompted by AFL-CIO criticism that the Reagan administration has been too soft in responding to the Polish government's military repression of the Solidarity free trade union movement.

The federation's 35-member executive council says the crackdown in Poland is Soviet-sponsored, and that the United States and other western countries should reply with strict economic sanctions, including a grain embargo, against the Soviet and Polish governments.

U.S. sanctions against Poland and the Soviet Union that President Reagan announced in December "fell short of the steps we urged," the council said Thursday in a resolution approved at its annual policy meeting. AFL-CIO President Lane Kirkland said today that Haig failed to persuade the council that it should abandon its position.

"I think the secretary of state fully understood our position before he came, and I think he still understands it," Kirkland said.

Kirkland added that the council "remained deeply dissatisfied with the concrete programs and policies" of the Reagan administration "on a wide range of issues."

However, Haig was equally unbending. He said that, although the United States was not ruling out the possibility of a grain embargo in the future and under different circumstances, the Reagan administration would not go along with the federation's suggestions.

An embargo might even help the Soviets obtain lower grain prices from other suppliers, and that "would be an unjustified punishment of the American farmer," Haig said. He said grain exports account for 75 percent to 80 percent of goods the United States sells to the Soviet Union each year.

In his remarks, Haig also went beyond previous administration comments on actions by Nicaragua, saying that recent photographs in the Paris newspaper Le Figaro "showed the most atrocious genocidal actions being taken by Nicaragua against Indians on their east coast." Corpses were visible in the pictures, Haig said.

U.S. officials have accused Nicaragua several times since late January of carrying out forced relocations and "repressive actions" against the Miskito Indians, who live near Nicaragua's border with Honduras. On Feb. 5, U.S. officials said they had heard reports of executions and the burning of villages in the area by the Nicaraguan army.

The Nicaraguan government, while acknowledging that it had relocated some Indians because they are in an alleged combat zone, has denied any repression. State Department officials said today that they were aware that the Paris newspaper recently carried an article on the situation, but the officials said they had not seen the article or accompanying photographs.

Haig came today, at Kirkland's invitation, to defend and explain the administration's foreign policy. But he also came with White House instructions to push President Reagan's economic program, which has been under attack here all week.

"He gave the council a long lecture on Reaganomics," said AFL-CIO chief spokesman Murray Seeger, recapitulating the unusually long closed-door meeting with a federation guest. "Haig spent a lot of time defending Reaganomics, taking the slightest opening in someone's question to defend the Reagan economics program," Seeger said.

Vice President Bush visited the council Tuesday on a similar mission.