THERE'S A LOGIC, but only a pathetic logic, to the administration's plan to sell 200 million pounds of surplus butter to New Zealand, the Big Enchilada of the international butter trade, which would then be in a position to sell that much more butter to the Soviet Union. Soviet plates are already heaped with American Bread (from American grain) and American mean (from animals fed on American grain). Why not American butter, too?

In fact, it is shameful to see the United States not only providing but, in butter, subsidizing the premium items in the Soviet diet, even while the administration tries to mobilize other nations against one Soviet invasion that has already taken place and another that could come at any moment. President Reagan justified lifting the Carter grain embargo on grounds of a campaign promise -- never mind that after the promise had been made the international scene was transformed by the Soviet attack on Afghanistan. In selling butter while the Red Army hovers over Poland, he would not have even that feeble excuse. Attempting to mask the ultimate consumer by passing the butter through New Zealand, moreover, fools no one and increases the subsidy, since New Zealand evidently will pay 20 or 30 cents a pound less than the $1.05 that butter brokers who deal directly with Moscow pay. For this butter the U.S. government itself paid about $1.50.

To be sure, it is primarily a Democratic butter mountain -- one built up by milk price supports granted in the last administration -- that looms over President Reagan, who has fought hard to trim subsidies to the dairy industry. But it is the Reagan administration that must suffer the embarrassment of demonstrating, again, that it is allowing domestic and political considerations to cancel out the important strategic aspect of a major export decision. How will it now undertake to add to the pressures that the United States and its friends can put on the Kremlin for the sake of Afghanistan and Poland? The Soviet wintertime diet is always short of fresh fruit and vegetbles. Perhaps the administration can see to it that the produce gap is filled, too.