Labeling U.S. charges as "lies," a senior Kremlin spokesman vigorously denied today that the Soviet Union was supplying weapons to Marxist guerrillas in El Salvador and said that there could be no Soviet-American summit if President Reagan insists on preconditions.

"I can tell you the Soviet Union has not and is not delivering weapons to El Salvador," Leonid Zamyatin, chief of the Communist Party Central Committee's international information department asserted at a press conference. He labeled as "lies" the State Department's special report that blamed Moscow and Cuba for supporting the guerrillas with arms.

Reagan "is absolutely incorrect" if he believes the report, Zamyatin said. "Lies repeated many times don't become truth."

Zamyatin, however, did not address the U.S. claim that the Kremlin and its East European allies had organized the shipment of arms from Vietnam and Ethiopia to Cuba. Cuba and the Sandinista government in Nicaragua, according to the State Department, were involved in the final transfer of weapons to the Salvadoran guerrillas to make it a "textbook case of indirect aggression by communist powers."

Zamyatin, a Central Committee member with close ties to Soviet leader Leonid Brezhnev, also asserted it is "incorrect to set preconditions" for a meeting between the leaders of the two countries. "We are ready and we are not posing any preconditions" on resumption of bilateral contacts at all levels, he said.

In his major report to the opening session of the 26th patry congress Monday, Brezhnev called for resumption of a "dialogue" to restore relations which have been frozen since the Soviet invasion of Afghistan in December 1979.

Reagan said yesterday in Washington that he is "most interested" in Brezhnev's invitation to meet, but said the issue of arming Salvadoran insurgents must be straightened out first. With a dig at communist archrival China, Zamyatin said this position of Reagan's "resembles hegemonism, it sounds like China. This is not our policy line."

Zamyatin accused Washington of forcing a "fascist junta" on El Salvador, and said a recent U.S. congressional delegation led by Rep. Barbara Mikulski (D-Md.) has reported that the population was being "decimated" by the Central American country's government.

"There are no Soviet advisers in El Salvador, but there are U.S. adviers," he said. "The U.S. ships arms to El Salvador; they don't hide it." These arms "destroy and kill a population that wants to live under its own choice of government."

Nevertheless, Zamyatin implied that the Kremlin had found signs that Reagan's response had not been totally negative and perhaps the door could be soon opened enough for low-level exploratory talks.

Escalating Brezhnev rhetoric that the "state of relations necessitates a dialogue," Zamyatin said there is "dire need" for wider contacts.

In fact, despite the high-level polemics and the Carter sanctions on most official exchanges and the grain embargo, the two countries have traded views at various diplomatic levels ever since the 1979 invasion. The sticking point, however, has been Afghanistan, and Brezhnev made clear in his report to the congress that Moscow has no intention of withdrawing its troops so long as there is armed resistance from the Moslem population to the Marxist government in Kabul.

Zamyatin said Moscow viewed West European reaction as generally positive to the Brezhnev address, especially his proposal for talks to enlarge the zone in which countries voluntarily notify others of troop maneuvers and invite foreign military observers.

"We can't discount the positive impact on the Madrid conference" this proposal may have, Zamyatin said, referring to the European security agreement's compliance review parley, where the Soviets have been assailed by the United States and other Western delegations for violating human rights and other guarantees.