The Soviet Union announced today that it was ending its eight-month moratorium on nuclear testing as a result of the underground test conducted yesterday by the United States.

In a statement issued by the official news agency Tass, the Soviet government said that as warned, the test in Nevada lifted the last condition for another extension of Moscow's unilateral moratorium.

"The U.S.S.R. declares that from now on it is free from the unilateral commitment made by it to refrain from conducting any nuclear explosions," the statement said.

"In the conditions that Washington is continuing its nuclear explosions, the Soviet state cannot forgo its own security and that of its allies," it concluded.

The Nevada test had been anticipated by the Soviets, who reacted with an official statement within minutes of the blast.

But while the Soviet media today roundly condemned the U.S. test, it was clear from other official signs that the public denunciations will not affect preliminary preparations for the next summit meeting between Soviet leader Mikhail Gorbachev and President Reagan.

The announcement of a May meeting between Foreign Minister Eduard Shevardnadze and Secretary of State George P. Shultz appeared in today's Soviet newspapers, along with ringing attacks on the Nevada test.

The end of the Soviet moratorium, which had begun last August and was extended by three months until March 31, had been foreseen in a speech by Gorbachev last week. Gorbachev said then that the Soviet Union would "regret" a decision to resume testing but that if the United States conducted another explosion after March 31, Moscow would have no choice.

In Washington, White House spokesman Edward Djerejian said the United States had "made it abundantly clear that we require nuclear testing for our security." He added that "the Soviets have been making preparations for some time now to resume nuclear testing. When they choose to resume is their decision."

The Soviets have stressed several times that the decision to keep the moratorium going has been a difficult issue internally. Officials have hinted privately at debates within the Soviet military where, as in the United States, they say many high officers have pushed for continued testing of nuclear weapons.

Since the U.S. position on testing was laid out early and seemed unlikely to change, most western diplomats here assumed that the Soviets pursued the moratorium largely for its public effect, both in the United States and in Western Europe.

Yesterday a commentator on Soviet television, Valentin Zorin, declared the moratorium "a political and moral victory" for Moscow, since it showed the Soviet Union was taking a real step toward ending the arms race.

The moratorium also served Moscow as another pressure point against Washington as the two superpowers circle the issue of arms control at the negotiating table in Geneva. It was one of two issues cited by Gorbachev in February as possible areas of agreement at the summit due to take place this year in the United States.

The government's official announcement declared that Washington's decision to proceed with yesterday's test had been greeted by "deep disappointment and general indignation" in the world.

The statement indicated that while this moratorium is over, the Soviet government would be ready "to return any time to the question of a mutual moratorium on nuclear explosions."

The Soviets again promised greater flexibility on the question of verification, noting that there should be "no insurmountable difficulties" on that question.

The Soviet Union "stands for the strictest control, right down to on-site inspections," the statement said. "Toward this end only one thing is needed -- the adoption of a political decision to terminate the tests."