How NICE IT would be if the United States

had ready a list of perfect sanctions to apply against the Soviet Union for violating international norms. These would bring the Kremlin instantly to its knees, and they would hurt the United States and its friends scarcely at all. You could give no more welcome a holiday gift to your favorite foreign-policy maker than a full matched set of perfect sanctions.

And now back to the real world. In that dusty realm all sanctions are imperfect. They hit the Kremlin, though not so hard as to make it buckle. They also impose a cost on the American, and Western, side. The great powers, in their mutual distrust, have been careful not to make themselves hostage one to the other. The balance of power is a balance of vulnerability, too.

The sanctions against the Soviet Union that President Reagan announced yesterday should be seen in this context. They will hurt but not cripple the Soviet Union. They will also inflict certain losses upon the United States and Western Europe. It was, however, essential to make clear in deeds Moscow's ultimate responsibility for the Polish army's crackdown on Solidarity. Not to make Moscow pay some price, and not to be ready to accept some sacrifice themselves, would make Americans collaborators of sorts. Especially is this so while Polish workers, using their chief remaining weapon, withhold their productive labor and while, it is reported, Solidarity's Lech Walesa may be entering negotiations with the regime. American sanctions against Moscow (and Warsaw) will weigh less than the Poles' own resistance to martial law. But Americans cannot let the Polish people struggle on alone.

West Europeans, as well as the Soviets, we trust, will pay close attention to the way Mr. Reagan is proceeding. He has moved by stages, not demanding allied partnership but consulting the allies as he goes. He gave the Soviets fair warning before imposing sanctions on them. What he asks of them is, by any mature standard, reasonable: to abide by their Helsinki word and to allow in Poland a course foreign to official Soviet taste but respectful of legitimate Soviet security interests. He holds out to the Kremlin the carrot of a fuller dialogue as well as the stick of still- tougher sanctions, presumably including the big-ticket item of an embargo of current grain shipments.

In recent years Americans have become decidedly more aware of Europe's greater stake in doing business as usual with the Soviets. They will not understand, however, why they should be more concerned than Europeans by the thrust of Soviet-sponsored military power in the heart of Europe.