The European Community today announced a wide-ranging list of American farm products that could be restricted if the United States acts against the EC over trade curbs stemming from the admission of Spain and Portugal to the community.

Spain and Portugal imposed limitations on imports of U.S. grain, soybeans, corn and sorghum March 1 as part of their terms of membership in the EC, which they joined in January. The United States says the measures could mean the loss of $580 million a year in American farm exports.

The Reagan administration said that unless compensation was received or the measures were lifted, it would place quotas or higher tariffs on a number of EC agricultural products. The U.S. restrictions are to be imposed in a two-step process beginning early next month.

Willy de Clercq, the EC commissioner for external relations, said in a statement outlining possible EC countermeasures that the community wants to "resolve this dispute without confrontation. But if the United States does decide to take the steps it has spoken of, it must be clear that the community will defend its lawful interests."

The community's list of U.S. products for possible retaliation was broken down into three categories, corresponding to the measures planned by the United States.

The first category includes sunflower seeds, honey, wine and bourbon. The second list includes fruit juice, beer and dried fruit, and the third includes corn gluten feed, soya cake, wheat and rice.

The total value of the U.S. trade in the products on the EC list is about $2 billion, an EC spokeswoman said, but she emphasized that the amount of trade affected by the community measures would depend on the restrictions imposed by the United States.

The EC products listed by the United States for possible restrictions include white wine, fruit juice, cheese, mineral water and pork.

De Clercq challenged U.S. assertions that American farm exports will be hurt by the Portuguese and Spanish measures. "The problems the United States fears from enlargement seem considerably exaggerated . . . ," he said.

[U.S. Trade Representative Clayton Yeutter said in Washington that any EC countermeasures would be unjustified. "The United States is not seeking a confrontation with the EC, but we will not allow our rights to be infringed upon," he said.]

The commission spokeswoman said that Deputy U.S. Trade Representative Michael Smith will meet with EC officials in Brussels next week.

High-ranking American and community officials will have another opportunity to discuss the dispute at a meeting of the Organization for Economic Cooperation and Development in Paris on April 17 and 18. Neither set of talks, however, is likely to involve substantive negotiations, EC and U.S. officials said.

The community, which wants the issue discussed in the context of the General Agreement on Tariffs and Trade, maintains that the United States ultimately will benefit from EC enlargement because of the lower tariffs the EC requires Spain to place on industrial imports.

The United States argues that it deserves immediate compensation for the EC measures and that the GATT process is too slow.