MOSCOW-Soviet Foreign Minister Andrei A. Gromyko said yesterday that planned U.S.-Soviet arms control talks would be "blown up" if the United States violates the commitment it made at Geneva to seek an accord on space weapons.

In a nearly two hour discussion with four prominent Soviet journalists broadcast last night on Soviet television. Gromyko renewed the Soviet campaign for a ban on development of a space-based missile defense, also known as "Star Wars."

Gromyko also said he told Secretary of State George P. Shultz during their meeting in Geneva last week that continued deployment of NATO medium-range missiles in Western Europe could jeopardize chances for success at the news arms control talks.

Gromyko rejected assertions from the Reagan administration that its $26 billion space-based Strategic Defense Initiative plan would be purely defensive. He said Moscow is being asked to rely on Washington's "conscience" to guarantee that the United States would not attack the Soviet Union once the antimissile system is in place.

Aggression

"These weapons are offensive and this plan as a whole, frankly speaking, is a plan of aggression. We are resolutely against it," he said.

Gromyko was asked what would result if the United States failed to uphold the spirit of the Geneva agreement on preventing an arms race in space, and he replied: "Those consequences would be most grave. If it (the United States) embarks on that path, the talks would be blown up. We made such a warning to the U.S. delegates."

He said he understood the U.S. position that it would be difficult to verify a ban on research into space-based weapons, but he said no one could guarantee that research would not lead to testing and then deployments.

The Soviet foreign minister said the Americans "pressed hard" at the Geneva meetings to prevent discussion of the space weapons issue, but the Soviet Union prevailed.

A joint statement issued by Shultz and Gromyko after the January 7-8 conference announced that the superpowers would set a date within one month to start negotiations encompassing strategic and medium-range nuclear missiles and space-based weapons.

"It is impossible to consider either the question of strategic armaments or the question of intermediate-range nuclear weapons without considering the question of space, or to be more precise, the question of preventing the arms race in space," Gromyko said.

He said the Soviet Union considers the three topics of the negotiations to be a single issue, and warned Washington against trying to discuss strategic and medium-range missiles without paying attention to space weapons.

"If no progress is made on questions of space, it would be superfluous to talk about the possibility of reducing strategic armaments," he added.