The Soviet Union today rejected U.S. protests that Soviet press coverage of the hostage neogtiations was "scurrilous," and accused Washington anew of using the now-resolved crisis as a pretext for adding to U.S. military strength in the Persian Gulf area.

In its first substantive foreign policy initiative since president Reagan took office, the Soviet Foreign Ministry denounced the earlier U.S. charges as "Unfounded . . . in actual fact, slanderous."

The statement, presented by the Foreign Ministry after Acting U.S. Charge d'Affaires Jack Matlock had been summoned there, also charged "The campaign around the question of the former American hostages, a campaign hostile to the U.S.S.R., is being kindled in the United States exactly in a bid to cover up plans to consolidate the U.S. military presence in the [gulf] as a means of gross pressure on the countries of the region."

Washington had bitterly protested Soviet press reports that came as negotiations for release of the 52 hostages neared an end two weeks ago. Soviet press and radio suddenly began saying the United States was about to launch an armed attack against Iran.

The U.S. Embassy here made several strong protests, and then-secretary of state Edmund Muskie bluntly rebuked Soviet Ambassador Anatoliy Dobrynin in Washington. The Soviets briefly modified their comments but then accused the Carter administration of deliberately prolonging the crisis, and followed up by saying the freed hostages had been "brainwashed" by the Central Intelligence Agency so they would deny having friendly feelings toward Iranians.