Soviet leader Mikhail Gorbachev, in his first major statement since he assumed power, said today that the Soviet Union was freezing the deployment of its medium-range weapons until November, awaiting a decision by the United States to follow suit.

Gorbachev said that he had made a "positive" response to President Reagan's proposal for a summit but that its time and place would be discussed further.

"I am convinced that a serious impulse should be given to Soviet-American relations at a high political level," he noted.

The 54-year-old leader announced in an interview with the Communist Party newspaper Pravda the unilateral freeze of Soviet medium-range nuclear missiles and the suspension of "other reply measures in Europe" to NATO deployments there. The interview was the first mention of a possible U.S.-Soviet summit in the Soviet press.

The tone of Gorbachev's remarks tonight, devoted almost exclusively to the arms race and U.S.-Soviet relations, was largely conciliatory and its language simple and direct.

"We regard the improvement of Soviet-American relations not only as an extremely necessary but also as a possible matter," he said.

The interview, to be carried in Monday's edition of Pravda, was read as the lead item of tonight's main Soviet television news program. Since taking office, Gorbachev has kept a low public profile, although on domestic issues his push for greater discipline and accountability has been amplified daily in the Soviet press.

Gorbachev's comments came as House Speaker Thomas P. (Tip) O'Neill Jr. (D-Mass.) arrived with a bipartisan congressional delegation hoping to meet with the Soviet leader on Wednesday and two days before Dutch Foreign Minister Hans van den Broek was to fly to Moscow for talks on the missiles issue.

[The Dutch Foreign Ministry reiterated Sunday night that the Netherlands would go ahead with deployment of 48 U.S. cruise missiles if Moscow has more SS20 missiles in place next November than on June 1 of last year, Reuter reported from The Hague. The Netherlands is the only NATO country scheduled to receive cruise missiles that has yet to make a decision on deployment.]

In going ahead with a moratorium on medium-range SS20 missiles, most of them in Soviet Europe, Gorbachev took the initiative on a longstanding Soviet proposal for a freeze on missile deployment in Europe.

The United States has argued that a freeze at current levels would give the Soviets an advantage. Since the mid-1970s, it is estimated that the Soviet Union has deployed 414 SS20s, of which about two-thirds are aimed at Europe. NATO began its deployment in the fall of 1983, and since then has installed more than 100 Pershing II and cruise missiles in Britain, West Germany, Belgium and Italy.

In reply, the Soviets modernized their nuclear weapons in Eastern Europe, replacing older missiles with SS12s and SS23s in Czechoslovakia and East Germany. They also moved nuclear-armed submarines closer to the United States

Tonight, Gorbachev noted that a continuation of the moratorium begun today after November depends on whether the United States stops its deployment of medium-range missiles in Europe.

Soviet president Leonid Brezhnev adopted a similar freeze on SS20 deployments, but that freeze was lifted when talks on medium-range nuclear weapons broke down in December 1983.

Gorbachev today noted that the new U.S.-Soviet arms talks in Geneva, begun last month on three separate categories of nuclear weapons, was a "positive fact."

But on Soviet-American relations in general, he said that while there is some reason for optimism, "there still is . . . plenty of what instills alarm."

"There are some shifts in other non-arms control fields of Soviet-American relations but very small ones," he said. "On the whole, relations remain tense."

Gorbachev said such tension has come to be viewed by some in the United States normal."We do not think so. Confrontation is not an inborn defect of our relations," he said. "It is rather an anomaly."

Gorbachev, following a Soviet line that has been consistent since last summer, said the U.S. proposal for a space-based defense system, known as "Star Wars," accelerates the arms race. He called the program "a screen to conceal the real and grave danger to our planet."

"They speak about defense but prepare for attack," he said. "They advertise the space shield but are forging a space sword. They promise the world stability but in reality strive to wreck the military balance."

Gorbachev also delivered a warning to U.S. allies considering a response to U.S. Secretary of Defense Caspar W. Weinberger's offer to join in a technological partnership on the Strategic Defense Initiative.

By characterizing the program "as nothing more than harmless research," which holds the promise of technological benefits, Gorbachev said, the United States is luring its allies into becoming "accomplices in this dangerous project."

The Soviets have made NATO allies the focus of their campaign against "Star Wars," seeking to capitalize on the uneasiness about the project expressed by some European politicians.

Gorbachev dismissed the view that a defensive system would make offensive nuclear weapons obsolete, arguing that space arms would only intensify the arms race.

At the beginning of the interview, Gorbachev identified capitalism and socialism as "two opposite social systems," but he noted that new states "with their own history, traditions and their own interests" should be allowed their right to choose their own road.

He said the arms race has reached a critical point: "Is it not time for those who shape the policy of states to stop, think and prevent the adoption of decisions that would push the world to nuclear catastrophe?"