A Soviet spokesman today rejected as a "cynical lie" Washington's claims that Moscow ignored a U.S. request to stop Libya from bombing a West Berlin disco.

But Foreign Ministry spokesman Vladimir Lomeiko confirmed that U.S. representatives went to the Soviet Embassy in East Berlin on March 27 with information about a planned terrorist attack. But he said they had no firm evidence.

At a press briefing today, Lomeiko said the claim -- made publicly yesterday by the U.S. State Department -- was an attempt by Washington "to wriggle out" of moral responsibility for the bombing of Libya.

Lomeiko said the Soviet Union knew nothing beforehand of the April 5 terrorist act in West Berlin, which President Reagan has said prompted Tuesday morning's raid on Libya.

"We possessed no concrete information on this matter. If we had obtained it, we would have shared the information," he said.

Lomeiko said Soviet representatives made it clear to the Americans that Moscow was opposed to terrorism but would not be drawn into an anti-Libyan campaign.

The Soviet Union has continued to dismiss American claims of proof linking Libya to the April 5 bombing of the West German discotheque, which killed an American Army sergeant and a Turkish woman. At a briefing yesterday, Lomeiko referred to the "so-called evidence," a word he said "can only be used in quotes."

Lomeiko today also said that the Soviet Foreign Ministry yesterday had notified foreign ambassadors that Soviet ships and planes would make full use of their right to pass through and over the Mediterranean.

The issue was raised in a series of meetings held to inform the ambassadors of the Soviet response to the bombing in Libya, diplomats said.

"The Soviet Union has full rights to use the Mediterranean for movements of its merchant and warships. It has made use of this right and will continue to do so," said Lomeiko today, confirming the account given by diplomats.

"The Soviet Union assumes the United States will take that fact into account in future actions," he said. Lomeiko said that by the Mediterranean, he meant both the sea and the air space above it.

Western diplomats here interpreted the assertion of Soviet right of passage as a sign that the Soviet Union will insist on its right to a Mediterranean presence.