THE SUDDEN summit that George Bush and Mikhail Gorbachev announced for next Sunday in Helsinki is being presented as an "informal unstructured" chat. Given the length and importance of the great-power agenda, you could not say the event had failed if that is all it turns out to be. But the very setting of such an event and the planning that necessarily goes into it is bound to bring Iraq to the center of discussion. The time has passed, if it ever existed, when Washington and Moscow could think of imposing a solution in a regional dispute. But the time has not passed for the two countries to think harder, together, about what they might do in this one.

For openers, Mr. Gorbachev could bring home the remaining Soviet military advisers in Iraq. The Kremlin has already announced halting Soviet military supplies to its erstwhile client, and it has supported American-backed resolutions in the United Nations, but removing the advisers would be a satisfying note. Beyond that, as Saddam Hussein settles into a waiting game of trying to distract everyone with selective hostage releases and diplomatic diversions, the superpowers need to polish a waiting game of their own -- tightening the isolation of Iraq and increasing its incentives to release all hostages and free Kuwait.

In his need for Western help at a moment when he is turning to radical economic reform, Mr. Gorbachev has a special interest in cooperation with Washington now. The Soviet Union also has legitimate interests in seeing calm restored to a neighboring region of particular concern to its own huge Moslem population. He can be expected to raise a question reflecting the nervousness recently expressed in Moscow about whether the American buildup in the Gulf will stay in place when the crisis ends.

For President Bush, the summit gives him an occasion to integrate his Gulf policy more deeply and closely with his Soviet policy, which necessarily remains at the center of American international concern. This needn't mean just more cooperation on Iraq, welcome as that could be. It means using the overlap of interest on Iraq to quicken progress on other large but, it appears, somewhat stalled items on the broader Soviet-American agenda, such as conventional force reductions in Europe as well as reductions in strategic arms. This would provide useful reassurance that the president is not allowing the Iraq crisis to divert him from relations with Moscow. He would be helping himself in American public opinion and strengthening the overall American position.