Soviet President Yuri Andropov called on the United States today to negotiate a ban on the use of antisatellite weaponry and announced Moscow's decision to impose a "unilateral moratorium" on the deployment of its "killer satellites" as a demonstration of its good will.

Andropov's new offer came during a meeting in the Kremlin with a group of nine Democratic U.S. senators led by Claiborne Pell of Rhode Island.

After the meeting, which lasted nearly two hours, Pell quoted Andropov as saying that the Soviet Union was "prepared to dismantle the existing antisatellite weapons systems" as part of an agreement banning "future development of such weapons."

The government news agency Tass quoted Andropov as proposing an agreement to the United States "on the elimination of the existing antisatellite systems and the prohibition of the development of new ones.

"The Soviet Union assumes the commitment not to be the first to put into outer space any type of antisatellite weapons, that is, it imposes a unilateral moratorium on such launchings for the entire period during which the other states, including the United States, will refrain from stationing in outer space antisatellite weapons of any type."

In Washington, State Department spokesman Alan Romberg pointed out that the Soviets "have the world's only operational" antisatellite system, but he said the United States would "study carefully any serious Soviet proposal on space arms control."

Moscow's antisatellite weapon, developed during the past decade, was described by western specialists here as an armed satellite hurled into orbit and guided into the proximity of its target. The United States is developing its own system, which involves a special missile lifted into the upper atmosphere by a F15 aircraft before it is aimed and fired at its target.

Military experts say that in time of war, one power would want to "blind" the other by disabling satellites crucial to communications, reconnaissance and navigation.

Diplomatic observers promptly suggested that the new Soviet offer must be put in the current context. The Soviet Union has developed and successfully tested a killer satellite while the United States is on the verge of testing its own antisatellite weapon.

During a meeting with journalists at the U.S. Embassy residence here, Pell suggested that Andropov's proposal may be a ploy designed to "forestall U.S. tests."

However, Pell said, Andropov's proposal "should be examined seriously to assess whether it is a genuine offer." Pell added, "We must hope that this moratorium is not a ploy but a step toward serious negotiations on eliminating these destabilizing weapons."

Andropov made his proposal during a wide-ranging discussion on various aspects of Soviet-American relations with the nine senators.

Pell described the conversation as a "substantive and good one." He said the 69-year-old Soviet leader had "an absolutely first-class mind" and appeared to be in "pretty good health."

Andropov's specific proposal on antisatellite weapons was preceded by a general statement of interest in a "complete" ban on the research and development of "any space-based weapons for hitting targets on Earth, in the air or in outer space."

Moscow's increasing concern about the militarization of space followed President Reagan's speech in March in which he called for a major American effort to use new technologies such as lasers to develop a system, possibly based in space, that could destroy incoming missiles.

Andropov's announcement of a moratorium and his call for talks on banning the use of antisatellite weaponry seem to be aimed at reviving discussions on the subject that had started during the Carter administration but that have been practically abandoned for the past four years. The Soviet leader's proposal for a general ban on weapons in space in April has received no response from Washington.

In his outline of Soviet policy, Andropov asserted that the Soviet Union wanted to improve its relations with the United States.

Andropov said that it would be "a dangerous miscalculation" if anyone entertained hope of attaining military superiority over the Soviet Union. Pell said the Soviet leader expressed his "strong dislike" for the planned deployment in Western Europe of new U.S. medium-range nuclear weapons.

Tass quoted Andropov as telling the senators that the future development of Soviet-American relations "depended" on reaching a mutually acceptable agreement at the Geneva talks on limiting medium-range nuclear weapons in Europe.

The deployment of 572 Pershing II and cruise missiles in five West European countries, which is scheduled to begin in December, "will have farreaching consequences which will inevitably affect the United States as well," Tass quoted Andropov as saying.

Andropov expressed the hope that an agreement at Geneva "was still possible if the United States showed an interest in an honest agreement based on equality." He said he would not accept an agreement that would prejudice Soviet security.

Speaking about Soviet-American talks on strategic weapons, also conducted at Geneva, Andropov described as "absolutely unrealistic" an attempt he attributed to the Reagan administration to "convince or compel" the Soviet Union "to break down the structure of its strategic forces and to reduce its basic components."

In the course of the discussion, the Americans raised several questions including the Soviet occupation of Afghanistan and human rights in the Soviet Union. They presented Andropov with several letters expressing concern about Jewish emigration, the fate of Baptists in the Soviet Union and the position of Soviet dissidents including the physicist Andrei Sakharov, living in exile in a provincial city, and the imprisoned activist Anatoly Scharansky.

No new ground was broken in these discussions, according to several senators.