Andrei D. Sakharov, who won the Nobel Peace Prize for his defense of human rights in the Soviet Union, called Friday for greater trust in Soviet leader Mikhail S. Gorbachev in his reform policies and in his commitment to broaden democracy and increase respect for human rights.

"An expression of trust in `perestroika' at this time would encourage it and also improve the human rights situation," Sakharov said, strongly endorsing Gorbachev's ambitious program of political, economic and social reform."We should even give an advance measure of confidence in (ts observance of) human rights," he said. "I believe that, as time goes on, there will be even further improvements."

Speaking at an unprecedented 90-minute news conference at the government press center, Sakharov said that "sizable changes have taken place" recently in the Soviet Union. And he credited Gorbachev with breaking away from the Stalinism that had gripped the country for so long.

"Mikhail Gorbachev is an outstanding statesman, and one of the chief architects of perestroika, one of the big doers in perestroika," Sakharov said. "From the bottom of my heart, I wish success for the cause with which his name is associated."

But Sakharov, a nuclear physicist who has been the spiritual father of political dissent here for two decades, said he had renounced none of his views and called forthrightly for wider human rights for Soviet citizens.

He seemed almost to be the leader of the Kremlin's "loyal opposition" as he addressed a packed news conference in the same hall where Gorbachev had spoken earlier in the week. His strong support for Gorbachev is likely to have a major impact here and abroad.

The news, however, lay as much in the news conference itself as in what the 67-year-old scientist said. For years Sakharov had been denounced by the government as a mouthpiece for the West for questioning Communist Party rule and championing human rights here. When he received the Nobel Peace Prize in 1975, he was branded a traitor to his country. He was sent into internal exile in 1980 for condemning Soviet intervention in Afghanistan and was allowed to return to Moscow only 18 months ago.

"That I find myself here reflects a change in this country," he said, "and not as a result of my having changed my position."

Sakharov, who has resumed work at the Soviet Academy of Science, has been lionized in the politically avant-garde weekly Moscow News. Quoted by other Soviet newspapers as well, he now expects to have some of his political works, which raised many of the same questions as Gorbachev has posed and put forward some of the same solutions nearly 20 years ago, to be published here soon.

Sakharov said he had agreed to no conditions for the news conference.