Andrei Sakharov today defied Soviet attempts to silence him, declaring from exile that he is ready to face "open and public" trial in place of the "gilded cage" of internal banishment to which he now is confined.

Sakharov, in a statement released by his wife, Elena Bonner, said, "I need the right to do my civic duty as my conscience dictates."

He said Soviet authorities are "trying to degrade and discredit me" in a way that "unties the government's hand for any future repression of dissidents inside the country."

Sakharov, who has been banished to Gorki, said the "main reason for my repression" was his recent series of statements condemning the invasion last month of neighboring Afghanistan. "The repressions taken against me were done at a moment of overall worsening of the international situation and an escalation in the repression of dissent internally."

These new world tensions, he said, were "caused by the U.S.S.R., culminating in the invasion, where Soviet troops wage a pitiless war against the insurgents and the Afghan people."

Sakharov said his isolation left his family defenseless and demanded that his mother-in-law, Ruth Bonner, and the fiance of his stepson be allowed to emigrate. His stepson already lives in the United States.

The Sakharov declaration was composed by his wife from mental notes she said she made in conversations with her husband before leaving Gorki for the train trip to Moscow yesterday. She said she did not write down what he wished to say because they feared police interception.

Although Bonner is officially not under the so-called administrative measure that applies to her husband and is ostensibly free to travel and visit freely, she said, "I think today's statement may be the last."

In his statement, Sakharov said "the authorities try to calm international public opinion by saying I will continue my scientific work and am not threatened with criminal charges." Sakharov has worked on astrophysics since breaking with the state more than a decade ago to take up the cause of human freedoms.

In closing, Sakharov declared, "I am thankful to all to have spoken up in my defense. My fate is fortunate, because it is possible for me to be heard. But I ask you not to forget those who independently work for human rights ..."

He mentioned a number of activists who have recently been seized by the KGB, including Gleb Yakunin, an Orthodox priest, and Tatyana Velikhanova and Viktor Nekipelov.

He proclaimed this as his philosophy: "I support a plualistic, open society that is both democratic and just. I support convergence, disarmament and peace, the defense of human rights throughout the world -- in our country and the countries of Western Europe, Indonesia, China, Chile -- everywhere a world amnesty for prisoners of conscience and the abolition of the death sentence."

Meanwhile, today, the Soviet Academy of Sciences, through its ruling presidium, officially censured Sakharov for "actions directed against the interest of our country and the Soviet people, actions helping heighten international tensions and denigrating the lofty title of Soviet scientists."

Sakharov last week was stripped of the awards and titles heaped on him during his years at the center of the Soviet hydrogen bomb program. Friends of the nuclear physicist had taken heart from the fact that those titles were removed by action of the Supreme Soviet, the rubber-stamp parliament, at the command of Soviet President Leonid Brezhnev, and that the academy traditionally free of direct intervention by the ruling Communist Party -- had not itself moved against Sakharov.

But the censure vote rolls back that faint hope of Sakharov's friends that he is immune from direct retaliation by the academy itself. Sakharov is still a member of the prestigious academy.

The 58-year old physicist and his wife were sent last Tuesday to Gorki, a city closed to foreigners 250 miles east of Moscow, in a Kremlin move that his further damaged its relations with the West in the aftermath of the invasion of Afghanistan.

"This is the first instance of internal exile without a trial in the Soviet Union since Stalinist methods were rejeted at the 20th Party Congress in 1956," Bonner said. "This amounts to a special regime that is worse than exile."

Bonner flatly rejected official allegations that her husband gave military secrets to Americans and other foreigners. "He never spoke to anyone at any time about any of this work," she said.

She said her husband believes there is no direct connection to his exile and the abrupt ouster the same day last week of Vladimir Kirillin, considered a liberal voice within the political-scientific hierarchy, from his powerful job as head of the state committee on science and technology and deputy prime minister. In 1973, when Sakharov was under bitter attack from the authorities, Kirillin met with the physicist and sought to persuade him to cease his dissidence and concentrate on science. Sakharov rejected the overtures.

Today, Tass announced Kirillin's successor, Gury Marchuk, 54, Ukrainian-born chairman of the Siberian branch of the Academy of Sciences based in Akademgorodok, the socalled "science city" at Novosibirsk.

There had been speculation that Kirillin either opposed oves against Sakharov, or the afghan invasion, or both, in the belief that Western countermoves would cut valuable ties and exchanges with Western scientist.