The Soviet chief of staff, Marshal Sergei F. Akhromeyev, confirmed that Moscow intends to resume nuclear testing after a U.S. blast in the Nevada desert last week. He told a news conference that the Soviets' eight-month-long, unilateral testing hiatus, formally ended last Friday, had caused a certain setback to Soviet military power. But he added: "The political gains in the struggle for a halt to nuclear testing . . . were greater than the purely military setback we suffered."