Moscow — In contrast to recent Soviet pessimism about US-Soviet relations, Soviet leader Mikhail Gorbachev yesterday extended his nation's freeze on nuclear testing and spoke as if a superpower summit would take place this year. Speaking on nationwide television, Mr. Gorbachev called on President Reagan to ``overcome his misapprehensions about the Soviet Union and its foreign policy'' and join Moscow in negotiating a nuclear test ban.
The Soviet Union, Gorbachev said, was confident that a test ban agreement could be reached quickly ``and can be signed this year at the US-Soviet summit.''
The extension of the moratorium to next Jan. 1 and the unqualified reference to the summit both came as a sharp change from the downbeat tone of recent official commentaries. These have tended to stress that any further extension of the moratorium -- first introduced on Aug. 6, 1985, and extended three times since -- should be a joint US-Soviet undertaking, not a unilateral initiative. They have also been very guarded in their reference to the chances of a summit's taking place.
But Gorbachev was careful to stress that the decision to extend the moratorium was not based on his belief that the Reagan administration had moderated its stance.
The US is maintaining a ``stubborn resistance'' to Soviet initiatives, Gorbachev said. For the past 40 years, the US has been the ``champion'' of nuclear explosions. And since the Soviet Union declared its moratorium, it has exploded 18 more devices, three of them, he alleged, unannounced.
He made no reference to the letter sent by President Reagan late last month on arms reduction. Soviet commentators have in the last week begun to say that the letter -- a reply to an earlier arms proposal by Gorbachev -- contained nothing new.
But in his speech Monday, Gorbachev also stressed that the decision was being made ``not from weakness but from an awareness of our high responsibility for the fate of humankind.''
``Don't count on scaring us,'' he warned the US, ``or pushing us into unnecessary expenses. If needed, we will quickly find an answer -- and it won't be the answer that the United States is expecting. It will be one that depreciates the value of `star wars.' ''
The unilateral test ban had given rise to some questioning in the Soviet Union, Gorbachev told television viewers.
But he ascribed the concern to letters from the public, not, as some Western observers have speculated, from the Soviet military.
If the US has not changed its position, Gorbachev's hopes of attaining a test ban agreement this year appear slim.
Reagan administration officials have consistently said that they are committed to a nuclear test ban in the long term, but that improved verification and significant arms reductions will have to come first.
But the moratorium extension does follow a meeting in Moscow last week of US-Soviet arms specialists.
Speaking shortly after the meetings, a US official noted that ``the overall tone and atmosphere'' of the discussions had been ``good.''
A second round of specialist talks is expected to be held soon in Washington. But US officials are also believed to feel that the chances of working out a detailed arms control proposal before a summit this year are very slim.