Soviet Foreign Minister Andrei Gromyko accused the United States today of seeking "to break the rough parity" between the strategic arsenals of the two superpowers and warned that the Kremlin would never permit this.

Gromyko said Soviet President Leonid Brezhnev has made this clear to President Carter at last June's SALT II summit in Vienna.

"We have repeatedly stated at the most authoritative level that we shall not allow this to happen," Gromyko declared in a speech to voters in the single-slate election campaign for the Russian Republic's parliament. "The capacity of the Soviet Union to defend the legitimate interests will continue to be maintained in a proper manner."

At the same time, the senior Politburo member continued the leadership's efforts at improving relations with Washington's NATO allies in the aftermath of the Soviet invasion of Afghanistan. "We confirm readiness to sit down at the table on questions of European disarmament if NATO recinds of cancels the December decision to base new medium-range missiles in Western Europe," Gromyko said.

"The convocation of a conference of military detente and disarmament in Europe would meet the interests of reducing military confrontation on our continent," Gromyko remarked. The Soviets, seeking to exploit U.S-NATO strains over the missile decision have suggested that the Americans are willing to sacrifice Europe in any limited nuclear exchange. The Soviets have tried to use Carter's Afghan invasion reprisals to argue that Washington is a careless troublemaker.

"Some figures in the U.S. capital are unable to put their disturbed nerves in order," Gromyko said in the deadpan sarcasm he relishes. "This is a pity. It would better if they took care of them. This is especially true with regard to those who are invariably cocky in their utterances addressed to the Soviet Union."

Carter has set Wednesday as a deadline for the Soviets to withdraw their troops from Afghanistan or face a U.S. boyscott of Moscow's cherished Summer Olympic Games.

In his remarks, which were televised nationally, Gromokyo asserted that "Washington policy turned toward the Cold War" as the 1970 ended. "It began long before the Afghan events, which brought political hysteria in the U.S., and has acquired particularly ugly forms [because of] the presidential election campaign."

He said American-inspired Western arms spending increases date from May 1978 and show the true direction of the Carter administration's policies.