MOSCOW, OCT. 19 -- Defense Secretary Richard B. Cheney, long one of the Bush administration's leading skeptics about the Soviet Union's reforms, ended a four-day trip to Moscow today saying that he is now "persuaded" that a new era of superpower relations has begun.

Cheney told reporters that he "began as a skeptic." But now, "if things continue" as they have in the past 18 months, he said, "it will be possible to say that we do not consider the Soviets as adversaries."

At a joint news conference, the Soviet defense minister, Marshal Dmitri Yazov, generally echoed his American counterpart's optimism but added that until both sides dismantled their nuclear weapons completely they would remain potential adversaries.

"If the United States is not our adversary, at whom are our strategic missiles aimed? Venezuela?" Yazov said. "Is the United States aiming theirs at South Korea?"

Cheney said that he did not try to persuade Moscow to sanction or aid any possible military operations in the Persian Gulf. Soviet Foreign Minister Eduard Shevardnadze has indicated that Moscow would send troops only as part of a United Nations contingent.

Cheney said the United States had still not given up hope that diplomatic pressure and economic sanctions eventually would force Iraq to withdraw from Kuwait, but, he added, "I also made it clear that we have not ruled out other options."

Yazov said he and Cheney talked extensively about "deep cuts" in conventional and strategic forces. He said that if Washington and Moscow, as expected, sign an agreement soon cutting their strategic nuclear forces by 20 to 35 percent, the Soviet Union could reduce its production of nuclear missiles by half.

Until strategic nuclear missiles are eliminated from each side's arsenals, Yazov said, Moscow will continue to replace around 10 percent of its rockets annually "to ensure readiness."

Cheney said he now regards himself as an "optimistic skeptic" about the Soviet military. He said that while the Soviet Union had clearly backed up its reform rhetoric by letting Eastern Europe go its own way and by consenting to the reunification of Germany, "that doesn't mean that I still don't have concerns about the Soviet military capability, because I do. . . . I am not suggesting that the United States should dismantle its strategic nuclear arsenal, because the Soviet Union retains a massive nuclear arsenal."

Cheney, who earlier had voiced strong doubts about shifts in the Soviet military posture said he now has a "positive impression" after his talks here with Soviet President Mikhail Gorbachev and Yazov and his trips to military installations, including a plant that produces MiG jet fighters. He did, however, express reservations here earlier this week about Moscow's plans to test four new-generation ballistic missiles to replace older models.

Asked about the proposed Soviet budget, which calls for unspecified cuts in defense, Yazov said he expected reductions of around 5 billion to 6 billion rubles ($8.3 billion to $10 billion at the artificially high official exchange rate). The 1990 defense budget was around 71 billion rubles ($118 billion), reduced by more than 8 percent from the year before.

Yazov was vague when asked about a recent reports that the Soviet Union had removed all nuclear weapons from the troubled "peripheral" republics outside the Russian republic. He said long-range missiles were based only in Russia, the Ukraine and Byelorussia, but made no allusions to shorter-range nuclear weapons.

The Soviet defense minister also dismissed rumors and reports in the Communist Party youth newspaper Komsomolskaya Pravda that conservative officers in the military, angered by budget cuts and the chaotic state of contemporary Soviet society, were planning to overthrow the Kremlin leaders who have brought about the changes.

"The armed forces of this country are part and parcel of our people and will never raise arms against our people," he said.