A spokesman for the Soviet military said today that the United States may have violated the 1972 Antiballistic Missile Treaty when it conducted an underground nuclear test in Nevada Saturday.

Speaking at a press conference held to counter U.S. charges of Soviet violations of arms control treaties, Lt. Gen. Vladimir Starodubov called the U.S. test a blow to hopes for a joint moratorium on testing.

He said the test in Nevada may have violated the ABM treaty since it did not take place at a site designated for testing defensive weapons. Pentagon and congressional officials have said that the Nevada blast was designed to test technology for the Strategic Defense Initiative, a proposed antimissile system.

Starodubov and Soviet Foreign Ministry spokesman Vladimir Lomeiko deplored the U.S. test as a step away from the commitment to arms control made by U.S. and Soviet leaders at the Geneva summit meeting last month.

"Right after the quiet religious holiday of Christmas, the first sound heard was a nuclear explosion," Lomeiko said. "After praying to the Lord God for quiet skies, the militaristic gentlemen carried out a test."

The Soviet Union's self-imposed moratorium on nuclear testing, begun Aug. 6, is due to end on Jan. 1 unless the United States agrees to join. The Reagan administration has rejected the moratorium, saying testing is a key element to the maintenance of defenses.

Lomeiko would not say whether the Soviet Union intends to resume testing after Jan. 1, but he said Moscow had shown its "good will and patience" in holding to the moratorium while the United States continued testing.

Lomeiko charged that yesterday's test, the 16th by the United States this year, was another step in a U.S. program to achieve military superiority over the Soviet Union.

He elaborated on a official Tass news agency statement reacting to the U.S. charges of Soviet treaty violations. He said the report, sent to Congress last Monday, was an attempt "to knock the wind out of Geneva."

"It is the U.S.S.R., and not the U.S.A., that has every ground to ask whether it is possible to trust" whether the United States "fulfills its obligations," Tass said.

The exchange of accusations comes as both sides prepare for the next round of arms control talks in the aftermath of last month's summit meeting between President Reagan and Mikhail Gorbachev.

Tonight, Tass characterized the American response to the moratorium -- the focus of a flood of articles and commentaries in the Soviet press during the past week -- as "evidence of Washington's real approach" to arms control.

The Soviet statement accused the United States of violating the ABM treaty with the installation of phased-array radar stations at the Thule Air Base in northern Greenland and at Fylingsdale, England. Both violate provisions of the treaty permitting defense systems only on the periphery, Starodubov said.

Peter Roussel, White House deputy press secretary, said "the United States is in full compliance with all arms control agreements and I don't anticipate us responding further until we have had a chance to study the substance, the full text, of their statement."

Starodubov, meanwhile, disputed U.S. claims that a radar under construction in Krasnoyarsk, Siberia, is intended as a missile attack warning system. "The radar under construction is for tracking space objects," he said, noting that the Krasnoyarsk radar "is not yet deployed, not yet developed and is only in the process of construction."

"We are ready to supply necessary information on the purpose of our radar," he said.

Starodubov disputed the U.S. argument that the Soviet SS25 missile is in violation of the SALT II agreement and charged that the United States was exceeding the treaty's limits on a single new strategic weapon by developing both the Midgetman and the MX missile.