IN HIS INTERVIEW with Time magazine, Soviet leader Mikhail Gorbachev comes across every bit as smart, organized and tough-minded as earlier appearances had indicated, with a lawyer's taste for adversarial dueling and a propagandist's touch for the rhetorical jugular. The American senators he received in Moscow yesterday appear to have gained a similar impression of a formidable figure at work.

Try as they might, Mr. Gorbachev told Time, he and his colleagues had been unable to detect the slightest flaw in Soviet policy: hence, if Soviet-American relations have poor prospects, it is entirely the American fault. To the extent that summits are debates staged for a world public, it is evident that Ronald Reagan is going to have to be at his best to hold his own in the November meeting of the two men.

It is also evident that Mr. Gorbachev is concerned about the gap growing between the American and Soviet approaches to the summit. He does not want the meeting to be focused on political dialogue or future agenda-setting of the sort of which the Reagan administration has been speaking lately. The administration has been seeking not merely to reduce its exposure to impatient public opinion but also to project a sense of modest aspirations in keeping with the real tensions between the two powers.

Mr. Gorbachev took note of recent American statements that sounded to him, he said tendentiously, "as if the stage is being set for a bout between some kind of political 'supergladiators'mand for one-sided Soviet concessions. To this he juxtaposed the Soviet view that the summit is designed chiefly for arms control negotiations.

Actually, there should be plenty of room at the summit for both sorts of discussions. Whether arms control, which is already under negotiation at Geneva, will be ripe for agreement or at least for a good nudge is something the Kremlin will have much to say about. Mr. Gorbachev, in fact, did say something -- something that may yet turn out to be important -- in the Time interview. He made explicit the previous Soviet hints that the Star Wars research Moscow insists on banning covers a verifiable "designing stage" of research and not an unverifiable "research in fundamental science," which, he conceded, "is going on (in the Soviet Union) and . . . will continue."

The leading unanswered question in Mr. Reagan's embrace of the Strategic Defense Initiative is whether, as he currently insists, he is truly bent on leaving a way open to deployment or whether he may be prepared to yield that up if Moscow accepts deep cuts in its first-strike-capable, land-based missile force. The signals that the shrewd Mr. Gorbachev is now sending to Washington will increase the pressure on President Reagan to weigh limits on Star Wars, if Moscow agrees to those deep cuts. For both leaders, the scheduling of a summit is forcing tough choices.