THE REAGAN-GORBACHEV summit stirred a set of cautious expectations for progress in various regional disputes, and nowhere more than in the Persian Gulf, where prospects for Soviet-American parallel action were already coming dimly into view. The Kremlin had publicly complained to Iran before the summit that Tehran was ''not doing anything'' to make good on its pledges to end the war. After the summit, a consensus statement issued by the Soviet president (for the month) of the Security Council moved the United Nations a notch closer to imposing sanctions on Iran to force it to comply with the U.N.'s cease-fire appeal of last July 20.

Is it more than smoke? The evidence is that the Soviet Union has experimented with having it both ways in the Gulf -- selling arms to Iraq while cultivating neighborly ties with Iran -- but that it is now under tightening self-generated and international pressure to go with the Arab side. The Iranians, it is now clear to almost everyone, including Moscow, were toying with the Kremlin. The Arabs have been increasingly forward in cooperating with each other, confronting Iran politically and demanding that Moscow get off the fence. Part of the reason for and the price of an improved Soviet connection with Washington is to cooperate in the Gulf. All of these considerations come on top of anxieties about having on the Soviet doorstep a growing American and Western military presence and a source of fundamentalist infection of its own Moslem population. This is what seems to be behind Moscow's hints at readiness to clamp an arms embargo on Iran.

The consensus is that before anything conclusive happens on the diplomatic front, Iran will launch a major new military offensive on Iraqi soil. The timing, targets and durability of this drive are the subject of much speculation, as is Iraq's capacity to blunt it. In some quarters it is referred to as the ''final'' offensive, the one whose military results would then be translated into the terms of a political settlement. It would be imprudent to count on an early end to a conflict that has raged for a period (seven years), with an intensity (nearly full, open-ended mobilization) and at a cost (a million casualties) defying all norms of the region. But current circumstances do at least raise a small glimmer of hope.