Soviet President Leonid Brezhnev today renewed his offer to negotiate reductions of Soviet nuclear missiles based in western Russia provided NATO did not go ahead with the scheduled deployment of U.S. medium-range nuclear rockets in Western Europe.

Brezhnev told Michael Foot, leader of the British opposition Labor Party, that Moscow is preparing to publish figures giving a breakdown on the arms balance, and he specified what a Soviet offer to extend East-West military confidence-building measures involves.

Foot quoted the Soviet leader as saying he was prepared to extend the current measures -- such as prior notice of major maneuvers and invitation of observers -- to all of European Russia provided the West extended them to cover all Western Europe, the coastal waters of Europe and the contiguous airspace.

The current measures, growing out of the Helsinki accords, are confined generally to Central Europe.

"I do not think that anyone could have been present at these discussions and not been convinced of Soviet sincerity in desiring to get these negotiations started and sincerity in wanting them to succeed," Foot told a news conference.

Evoking visible satisfaction on the faces of Soviet officials in the auditorium, Foot said he had raised the issues of Poland, Afghanistan and human rights during his visit but asserted that "we have never held the view that these events should prevent us from seeking arms-control agreements."

He added that in the search for these agreements "we must not be distracted by any event whatsoever."

Foot's endorsement of the Soviet position was seen as an important Soviet achievement in mobilizing opinion in Western Europe against the deployment in 1983 of U.S. cruise and Pershing II missiles.

Brezhnev spent about 80 minutes with Foot and Denis Healey, the deputy Labor leader, outlining the Soviet position. As reported by the two Labor leaders, this amounted to a restatement of Brezhnev's 1979 offer to reduce the number of new SS20 missiles in western Russia if the U.S. missiles were not deployed.

Despite that offer, NATO decided to deploy the new U.S. weapons in Britain, West Germany, Belgium, the Netherlands and Italy. Since then, however, the allies have made negotiations on limiting medium-range weapons in Europe a precondition for acceptance of the missiles.

Foot said Brezhnev showed him a report on Soviet military strength. "I looked through it but did not have time to study it in any depth," Foot said. "Mr. Brezhnev said it would be published soon," possibly tomorrow.

Foot said the Soviet leader should not be blamed for not going all the way--he had gone part of the way and moves toward disarmament had to start somewhere. When asked about details, Foot said his delegation had not been in a position to negotiate, but to encourage talks.