West German relations with leftist groups in Central America have drawn U.S. concern and raised questions about German aims in that politically volatile part of the world.

Traditional German involvement in Latin America has centered on trade relations with larger countries like Mexico, Argentina and Brazil. But the United States fears what it perceives as a bold tilt to the left in Central America by Germany's ruling left-center Social Democratic Party.

The Bonn government itself has appeared reluctant to support U.S. efforts in El Salvador by so far refusing a specific U.S. request to give aid to that country's faltering civilian-military junta.

U.S. sensitivity to outside involvement in Central America was heightened by last year's Nicaraguan revolution.Now, internal leftist opposition to the Salvadoran junta and the rightist military government in Guatemala have raised new fears in Washington that Carter administration efforts in the region could be countered by actions of its European allies.

Bonn government officials said in interviews they have no intention of undercutting U.S. policy in Latin America. They said they recognize it is a region of vital interest in fostering stable governments there that are sympathetic to the West.

But there are differences in deciding just how to do this. Of immediate concern to Washington is persuading Bonn to give aid to the new military junta in El Salvador. Bonn closed its embassy there during the government upheaval that began with a coup last fall -- a move that West Germany Foreign Military officials say was done for safety reasons and not for political ones, although it was regarded by some as a political move.

Meantime, Germany's Social Democratic Party has kept its ties to El Salvador's Social Democratic groups, which first joined the new junta last October and then charged its military component with repression and split from it early this year to go with the most extremist leftist opposition parties. While Washington moved to support a new junta formed by the military and center Christian Democratic groups, the Bonn government gave the El Salvador regime little chance for survival.

Despite U.S. pleas that Bonn assist El Salvador, $14.1 million in aid that the West German government had pledged mostly for rural projects in the country has been frozen. Officials at Bonn's Economic Development Ministry say conditions in El Salvador are not safe enough at the moment to risk sending experts to plan the projects.

The general story of Germany involvement in Central America is further complicated by the varied nature of the activity. In addition to Bonn's formal diplomatic ties and an official German program of development aid to Latin America, the Social Democratic Party and its well-endowed Friedrich Ebert Foundation conduct foreign relations of their own, often sympathetic to leftist causs.

The distinction between bilateral party relations and Bonn government policy is sometimes difficult to make.

The Ebert Foundation spends between $5.5 and $7 million a year in Latin America, according to foundation officials. For the most part, the money -- like that spent by its active, conservative opposition, the Konrad Adenauer Foundation of Germany's Christian Democratic Union -- goes toward political education and development aid programs.

What has irked Washington officials is that the invited guest lists for some Ebert Foundation political seminars have read like a who's who of leftist forces in Central America, giving a sort of legitimacy to some groups the United States would rather not see encouraged.

The foundation has also been criticized for publishing educational material that promotes Marxism and for sending Roshan Dhunjibhoy, a leftist well-known in German film-making circles, in Jamaica to teach a film course Jamaican opposition leader Edward Seaga charged that Dhunjibhoy is a known communist sent by the Ebert foundation to radicalize the mass media.

In addition, top German Social Democatratic leaders have themselves done things to fan U.S. irritation, Party Chairman Willy Drandt, serving now as chairman of the Socialtist International, presided over a Latin regional conference in March that condemned the government in El Salvador and blasted U.S. support for it.

U.S. annoyance about all this was expressed to Social Democratic Party Deputy Chairman Hans-Juergen Wisehnewski when he visited Washington in July for talks at the White House and State Department. In an interview after he returned, Wischnewski said he was surprised at the degree of U.S. concern about what his party was up to in Cenral America, giving the impression that he and other party leaders -- including Chancellor Helmut Schmidt -- had not paid much attention to the matter.. He said Central American initiatives had not been among the party's highest primities

Subsequently, Bonn Foreign Ministry officials said they would be sending a charge d'affaires to reopen the German Embassy in El Salvador. Foreign Minister Hans-Dietrich Genscher said that otherwise the "moderate ruling junta" -- a descriptive term for the government there used by the United States -- would be toppled by forces seeking a revolutionary development."

But according to a senior official in the Economic Aid Ministry, the money is still frozen.

When the Nicaraguan foreign minister, the Rev. Miguel D'Escoto visited Bonn last week, Genscher seemed to go out of his way to declare West Germany's interest in supporting the U.S. position. While D'Escoto warned against "interventionist tendencies emerging in the United States," Genscher said Bonn wanted to help ease the strained relations between Nicaragua and the United States.

One reason for Bonn's shift on El Salvador and the open stress on support of U.S. aims in Central America is fear here that the United States might intervene more directly if the political situation in the region deteriorates further. "We are interested in avoiding deterioration so that there is no clash," said a Bonn Latin American expert, adding, however, that he had no indication that Washington is considering intervening. "We must stay interested in making sure the United States does not get into too difficult a position in Central America" he said.