At the Geneva summit meeting, Soviet leader Mikhail Gorbachev apparently tried to convince President Reagan that to Moscow, Reagan's Strategic Defense Initiative (SDI) looks like an attempt to put into space offensive weapons that could attack targets on Earth.

Gorbachev's new line of attack against the program, often called "Star Wars," emerged in postsummit comments by both leaders, and it apparently made an impact on Reagan. The president told a group of columnists and television anchors after his return from Geneva that Gorbachev "really believes that . . . whatever you were trying to discover about a defensive weapon or system could possibly lead to learning things that could enable you then to put offensive nuclear weapons circling the earth."

White House chief of staff Donald T. Regan told the same group that in the plenary session on arms control in Geneva, "their main thrust was that they honestly believe that what we're trying to accomplish is not what we're saying . . . and that we are trying to find a weapon that we can put in space under this guise that will become another form of offensive weapon that will not only shoot down ballistic missiles, but buildings as well."

In attacking Star Wars this way, Gorbachev appeared to be reflecting one approach of a recent anti-SDI document published in Moscow that Soviet scientists are circulating to their English-speaking colleagues. It says that "space-based strike weapons which are being developed in the U.S.A. appear to be intended not only for knocking out the other side's satellites and strategic missiles after their launch, but also as preemptive weapons to be used against ground targets, for performing the first strike."

At his postsummit news conference in Geneva, Gorbachev appeared to show patience with what the president has called his "dream" for a nuclear shield while putting it down as an unacceptable threat to his country.

Speaking of SDI, Gorbachev said, "The president considered it to be a shield, but we have shown, I hope convincingly, that these space weapons could be used equally against missiles, against satellites, and against facilities on Earth."

Gorbachev said he told the president: "Bear in mind, Mr. President, you do not have simpletons sitting in front of you."

Gorbachev said the Soviet leadership studied the idea of undertaking its own SDI-type program, going as far as discussing "what weapons to take into space."

The answer came back, he said, "We are against the race."

He said they also studied what they would do if the United States rejected the Soviet approach and a space-weapons race resulted. "Our response," he said, "will be effective and less expensive, and . . . can be implemented in a shorter period."

To calm Gorbachev's concerns, Reagan said he "told him, first of all, we would have the open laboratory concept, where if anything like offensive weapons was developing, they'd know it as soon as we did."

Furthermore, Reagan said, "My vision of this was that if such a defensive system is possible, then you don't rush out and deploy. You sit down with them, you sit down with our allies, literally with the world, and make this available to the whole world in return for the elimination of all nuclear offensive missiles."

Reagan said Gorbachev responded that if nuclear weapons were to be eliminated after Star Wars proved feasible, "Why would we need to even go forward and try to find such a defensive system?"

Reagan said he responded that "in a later generation . . . there may come a madman . . . that would reintroduce nuclear weapons."

Gorbachev was particularly contemptuous of the open laboratories idea. "What has been suggested to us," he said at the news conference, "is something like: Let us open up the laboratories and monitor how the arms race is going.

"This is naive," he said. "The starting point is fallacious and unacceptable."

The Soviet leader said that if a ban on weapons in space is reached, "we are prepared on a mutual basis to open our laboratories for monitoring an accord of that kind."