The European Community, signing a cooperation accord with six Central American nations today, reaffirmed its disagreements with U.S. policy by declaring that social and economic problems were the fundamental cause of tension in the region.

In a series of joint communiques issued with six Central American nations and the four neighboring countries that make up the Contadora group, EC foreign ministers also called for the elimination of the "foreign military presence" in Central America, and appealed to "all countries with links and interests in the region" to help create favorable conditions for the success of the Contadora peace initiative.

Community officials said the latter appeal was directed at the United States and the Soviet Union.

The communiques did not single out Reagan administration policies for criticism, but reemphasized the differences between the administration and its European allies on the root causes of instability in Central America and how it should be dealt with.

The administration has identified the Nicaraguan government and its Soviet and Cuban backers as the chief cause of tension in the region and has given military support to forces fighting the Nicaraguan government. The EC joint communique said "economic imbalances and social injustice" are "in large measure, at the root of political instability" in Central America.

The communique added that conflicts in Central America could "not be resolved by force," and called for an end to "action designed to intimidate and bring about destabilization, such as terrorism, subversion and sabotage."

The declarations were hailed by Nicaraguan Foreign Minister Miguel d'Escoto, who attended the meeting along with foreign ministers of the other nine nations, as condemnation of what he termed "U.S. aggression" against Nicaragua.

The communiques agreed to by Nicaragua, however, also committed the leftist Sandinista government to guarantee democratic liberties and work for national reconciliation.

Nicaragua has been by far the largest recipient of community economic aid to Central America in recent years, and the EC member states have not participated in the U.S. trade embargo against Managua that began last May.

The United States irritated the community last year when it asked the EC not to give assistance to Nicaragua just as preparation of the accord was beginning.

Most of the aid under the new five-year cooperation accord will go to Central American regional organizations, rather than to governments, community officials said. The agreement commits the community to increase substantially the amount of its aid, which in the past several years has averaged about $33 million annually.

The EC agreement was criticized by Alfonso Robelo, the director of the United Nicaraguan Opposition, a U.S.-backed anti-Sandinista group. Speaking at a press conference here, Robelo said that aid to Central American nations should be conditioned on their support of pluralism and social justice.

The Nicaraguan government, Robelo said, did not meet those conditions because of its "totalitarian nature."

The signing of the cooperation agreement between the community and El Salvador, Nicaragua, Honduras, Costa Rica, Panama and Guatemala represented a tentative step by the EC to increase its involvement in a region that historically has been dominated by the United States.