In a speech delivered on the eve of the U.S. elections, Soviet President Konstantin Chernenko again put the blame for international tensions on Washington.

Addressing a group of youth leaders from communist countries, Chernenko stressed that "the course of an arms buildup and confrontation . . . is not our policy."

"And if the world situation causes alarm, responsibility for this is borne fully and entirely by the imperialist reactionary forces led by the U.S.A.," he said.

"It is the U.S.A. and its allies that have set themselves the insane goal of achieving military superiority over socialist countries. Naturally, we cannot allow this to happen, and we shall not allow it," he said.

Chernenko urged Soviet Bloc youth leaders to beware of the "massive psychological warfare unleashed by the imperialist forces against socialist countries." He said Young Communist League leaders should work to eradicate "everything that is incompatible with socialist justice, collectivist principles and work morality."

Chernenko's comments on U.S. policies came as the Soviet media continued to hint at the complicity of "reactionary imperialist forces" in the assassination of Indira Gandhi and to assail President Reagan's arms control record.

As the U.S. election neared, Soviet press commentary has tended to downplay differences between the two presidential candidates.

A preelection report from Washington, shown on Soviet television tonight, said that the leaders of the Democratic Party had not put forward "realistic alternatives" to Reagan's policies, confining themselves to "superficial criticism." As a result, the reporter said, the Democrats failed to seize the initiative "as tomorrow's elections will show."

The election, the reporter said, has become a personal competition between people whose programs are more or less the same.

During recent weeks, the Soviet press has speculated on Reagan's plans for a second term, apparently assuming his reelection. A recent commentary in the official news agency Tass, examining Reagan's proposal for a special ambassador to break the U.S.-Soviet impasse, accused the president of assuming "the garb of a peace-maker" during the campaign.

An article in the government newspaper Izvestia noted this week that the 1984 elections would be the most expensive ever, with campaign costs rising at a rate outstripped only by "military appropriations and the national debt."