The two top agricultural officials of the United States and the European Community agreed yesterday that growing farm-trade tensions between them must be reduced, but then each proceeded to escalate the argument a bit.

U.S. Agriculture Secretary John R. Block told reporters he intends to step up his contacts with EC agricultural officials in an effort to resolve differences and ease tensions that he called a threat to trade relations.

But Block insisted that the United States will continue its new $2 billion farm export subsidy program as a counter to EC export subsidies, and he termed "absurd" an EC reaction to a U.S. decision to put a duty on pasta imports from Europe.

Block earlier singled out the EC as his target as he announced that up to 1 million tons of U.S. wheat would be offered to Algeria -- a market captured by the Europeans -- in the first subsidized sale. He said yesterday that Algeria still has not made a tender and that he could not predict when or if it would.

But the secretary said the Reagan administration intends to make more offers for subsidized sales where the United States feels it has been undercut by unfair trading practices of competitor nations.

For his part, Frans Andriessen, the chief agricultural officer of the EC, agreed on the need for easing tension. But he also criticized U.S. farm policy, said he didn't like U.S. targeting of the EC and predicted that the community will impose duties on American lemons and walnuts as a reaction to the pasta case.

"The United States took unilateral measures and the community reacted. . . . We have just replied to that," Andriessen said. "Sometimes you need an aggravation before you can resolve these things. . . . Let's hope this creates conditions for discussions to end that dispute."

But Andriessen, here for talks with Block, Secretary of State George P. Shultz and U.S. trade officials, warned that concessions must be made by both sides before the EC and the United States can bury the hatchet over farm trade and export subsidies.

Andriessen also said the EC had little reaction to the U.S. decision to begin a subsidized export program, although it "didn't appreciate" Block's singling out of the community. He said there could be more reaction, however, after more details of the U.S. program become known.

Block said that he had told Andriessen that the United States will be flexible in its attempts to force changes in EC agricultural policy. He also said the United States will need time to cut farm spending and bring about the changes in policy sought by the administration to make U.S. exports more competitive.

"A long time-frame is likely for both of us," Block said. "Seven, eight, 10 years to bring the whole thing down. Tensions have to be brought down."

"We really ought to sit down and bring a halt to this whole thing. . . . There is good support for that among the agricultural ministers of the EEC. They see the risk of international trade without rules. It can be chaotic."

With U.S. agricultural exports down $10 billion since their 1981 peak of $43 billion, Block is under heavy political pressure to take steps to regain export markets that farm-state legislators and farmer organizations claim have been lost to subsidized farmers from other countries.

Block and others have identified the EC as a chief villain in spiriting away U.S. markets, but Andriessen said yesterday that the community's world market share of grains had remained stable for the last four years. "The United States is losing," he said, "but it's not losing to the community."