Soviet leader Mikhail Gorbachev today used his first domestic speech since his summit meeting in Geneva with President Reagan to renew a sharp attack on Reagan's Strategic Defense Initiative, which Gorbachev described as "the main obstacle to agreement on arms control."

While telling the Supreme Soviet that "the overall balance sheet of the Geneva meeting was positive," Gorbachev appeared to temper the conciliatory tone that he and Reagan struck in their closing joint appearance in Geneva last Thursday.

While the two leaders agreed in their joint statement in Geneva not to seek military superiority, Gorbachev today accused the United States of doing just that. And the Soviet leader again established agreement on banning space weapons as a precondition for carrying out the kind of reductions in offensive missile systems that he and Reagan jointly praised in Geneva.

"It is absolutely essential to slam the door through which weapons could get into space," Gorbachev told the 1,500 delegates of the Supreme Soviet in an hour-long Kremlin address today. "Without this, radical reductions in nuclear armaments are impossible."

In the face of a continuation of U.S. research on SDI, a space-based antimissile system popularly known as Star Wars, he continued, "the Soviet Union will have to improve the accuracy and to raise the yield of its weapons so as to neutralize, if necessary, the electronic space machinery of Star Wars."

Gorbachev, whose audience included representatives of the Soviet military, assailed the U.S. commitment to SDI in a harder tone than he used in his speech at the end of the summit last Thursday.

"The American administration is still tempted to try out the possibility of achieving military superiority," he said. "But we will find a response!" he shouted, and the applause drowned him out.

But in his overall summit report to the Supreme Soviet, the country's highest legislative body, which enacts programs directed by the ruling Communist Party, Gorbachev gave an optimistic appraisal of his two days of talks last week with Reagan. "We have every right to say that the overall balance sheet of the Geneva meeting was positive," he said, adding that the meetings were "frank to the utmost."

Gorbachev said that both the U.S. delegation's approach and the personal contact with Reagan added to the constructive summit results. "The position of the American side," he said, "included certain elements of realism that helped resolve a number of questions."

Calling the dialogue begun between him and Reagan at the summit "a stabilizing factor in itself," Gorbachev said, "We appreciate the personal contact established with the president of the United States."

Gorbachev listed three ways in which the Soviet Union and the United States should start paving the way for results at their next summit meeting, scheduled for next year: compliance with the 1972 Antiballistic Missile Treaty, adherence to the "relevant provisions of the SALT II accord," which expires at the end of this year, and acceleration of the arms talks in Geneva, as the two leaders agreed in their joint statement.

He also said Moscow is prepared to extend its moratorium on nuclear testing, due to expire in January, if the United States concurs.

Gorbachev struck a defensive tone in explaining why he felt obliged to carry through with the summit. Secretary of Defense Caspar W. Weinberger and "extreme right-wing forces" sought to "thwart the meeting" or "at least to make it meaningless," he said. Such forces had charged Reagan with the task of "forcing us to alter our system, to revise our constitution," he said.

He said that from the beginning of its term in office the Reagan administration "assumed a course of confrontation while rejecting the very possibility of a positive development of Soviet-American relations."

He cited testing of an antisatellite missile, "speedy deployment of Pershings in West Germany," and adoption of an "all-time record military budget" as presummit U.S. provocations.

Gorbachev also reported "diametrically opposite" interpretations between the superpowers on how regional conflicts occur and should be solved. The United States, thinking in terms of spheres of influence, he said, "reduces these problems to East-West rivalry."

"We cannot accept this interpretation," he said. "We have been and remain on the side of peoples upholding their independence."

The policy statement was interpreted by western analysts here as a firm defense of the Soviet Union's support of military conflicts in Afghanistan, Angola, Nicaragua and other Third World trouble areas.