U.S. Ambassador Deane R. Hinton said today that the United States would stand by the democratic verdict of the March 28 elections here, but made it diplomatically clear that a victory by the far right could endanger continued U.S. economic and military aid.

Speaking at a press conference in his tightly guarded embassy here, Hinton left little doubt that Washington is hoping for an electoral victory by the Christian Democratic Party of Jose Napoleon Duarte, now president of El Salvador's governing junta.

Hinton said U.S. public and congressional support for the continuation of already controversial aid to El Salvador would depend primarily on "what actions and policies would be followed by the new government," which will be named after the election.

"But, of course, an extreme government, an extremist government, could complicate the problem of public support for aid in the United States," the ambassador said.

The election will select a constituent assembly that is expected, among other things, to draw up a new constitution. The assembly is also expected to use its self-determined mandate to name a new government to replace the current junta, which has ruled since a coup by young officers on Oct. 15, 1979 overthrew an old-line military government.

Hinton's comments today followed his delivery of a prepared statement in support of the election, which he termed "the most revolutionary event in recent Salvadoran history." His remarks were as close as the United States has come thus far to warning Salvadoran voters of the consequences of voting for candidates of the extreme right, represented by retired major Roberto D'Aubuisson's National Republican Alliance. D'Aubuisson has been accused of ties with one of the secret rightist "death squads" which blamed for much of the violence here that has decimated the ranks of both moderate and leftist politicians and their supporters.

D'Aubuisson's party has shown surprising strength in the election campaign and has thus emerged as the biggest challenger to Duarte's Christian Democrats. Both the extreme and moderate left, fighting the government in a coalition of guerrillas and politicians, are boycotting the elections.

The U.S. ambassador has been meeting privately with candidates and political leaders participating in the race to urge the necessity for accepting the verdict of the voters no matter which way it goes.

Asked what he would do if an extremist won, the ambassador insisted he would still try to work with him, although he added that it would be up to the Congress, and the U.S. public, to determine the extent of support for El Salvador's government in the future.

"Let me say that even if somehow the Communists had decided to participate in the election and won, we would have tried to work with them," the ambassador said to a group of foreign and local journalists. "We respect the democratic process and I'm here to tell you, as a representative of the U.S. government, that no matter who wins these elections, I will do my damnedest to work with them to develop areas of common interests for the good of this country and in the national interests of the United States."

With the boycott, the Christian Democrats represent the most liberal group participating. Six other parties, including D'Aubuisson's, also are contesting the election.