Yeltsin Extends Russia’s Ban on Nuclear Testing : Weapons: In public appeal, president also calls for an international treaty fully barring all such tests.

President Boris N. Yeltsin on Monday extended Russia’s ban on nuclear testing through July, 1993, and his defense minister said the moratorium could run for all of next year if the United States follows suit.

If all the nuclear powers announce similar test bans, “there will be a real chance for the realization of humanity’s old dream--a full moratorium on nuclear testing for all time,” Yeltsin said in a public appeal.

The Russian president particularly called on Britain and China to stop testing, now that Russia, the United States and France have all moved in that direction.

France announced in April that it would stop its nuclear tests. In Washington, the White House continues to oppose bans on nuclear weapons testing, but Congress passed new legislation Oct. 2 that included provisions halting underground tests by the United States for nine months and imposing a total moratorium by 1997.

Although President Bush signed the bill, he also promised to seek new legislation in the future to permit underground nuclear tests. On Monday, responding to Yeltsin’s initiative, the State Department repeated Bush’s argument earlier this month that “we (the United States) must continue to conduct a minimal number of underground nuclear tests, regardless of the actions of other countries.”

Yeltsin’s moratorium continued the unilateral one-year test ban that then-Soviet President Mikhail S. Gorbachev’s declared last October. But it came as something of a surprise in light of Yeltsin’s decree last spring that Russia’s only remaining test site, the island of Novaya Zemlya in the far north, should be kept technically ready to handle tests.

Resistance among residents of the territory around Novaya Zemlya to further explosions may have spurred his decision to extend the ban, according to Alexander Konovalov, an expert on arms control at the prestigious Institute on the U.S.A. and Canada.

But the main force behind the extension, Konovalov said, is “the understanding on the top level that we’re on the edge of a dramatic reconsideration of all the stereotypes of the nuclear age”--including the belief that periodic tests are needed to ensure that weapons are still in working order.

A spokesman for the Foreign Office in London gave that reason for Britain’s refusal to join the ban. He said Monday that testing is necessary to ensure the weapons’ safety and that Britain could not reduce the number of tests without eliminating the weapons entirely.

The last nuclear test on Novaya Zemlya is believed to have been conducted in 1988, but the area remains controversial. A Greenpeace research vessel seeking to test for contamination in the waters near the island was detained by Russian authorities last week on charges of violating the border, and at last report it remained in custody.

Yeltsin’s decree extending the test ban cited the many requests he had received from lawmakers, ordinary Russians and “individual citizens of various countries,” and also “the significant damage already done to the environment.”

He called for an international treaty fully banning all nuclear testing and said Russia is ready at any time for talks to that end.

Russian Defense Minister Pavel Grachev told the Itar-Tass news agency that Russia is willing to extend the moratorium through the end of 1993 if the United States does the same.

“However,” he said, “a moratorium cannot be unilateral permanently. If we do not reach accord, Russia, evidently, will resume nuclear tests in the middle of 1993.”

Arms control negotiators have long given fairly low priority to weapons testing, concentrating instead on cuts in missile arsenals. But Konovalov said mounting public pressure from Russians and Americans could soon gain enough momentum to bring about talks on a worldwide test ban.

“I do believe we could live without nuclear tests at all,” he said, “but it should be done not through a series of unilateral steps but through negotiations.”

Times staff writer Jim Mann in Washington contributed to this report.