Argentina appears to be paying extremely heavily, in battle, for its invasion of the Falkland Islands. Such are the workings of modern technology and chance that it is a gamble to say the British can wrap up the war as easily as some officials are predicting. Yet the statements and silences of the two sides indicate that currently the battle is going Britain's way. The qualities of British arms are there to see, and the Argentines have not shown they are a match.

This is not to rule out all possibility that a stalemate or something worse could overtake British fortunes. At the moment, however, the military trends are daily sharpening the question of what Britain will do if it wins. Over the weekend, officials indicated they had not given it their full attention. They are now working on it, but their latest formulations, we trust, are not their last.

Prime Minister Thatcher, determined not to let her forces' momentum be halted prematurely, has hardened the conditions of a cease-fire. She now declares that a truce depends on an Argentine surrender and full withdrawal; other officials speak of a "total surrender." It is easy enough to see why a leader who had committed troops to battle would want to define a military objective commensurate with the cost and sacrifice entailed in achieving it. But even if the British people are prepared for that measure of sacrifice, it must be asked whether it is relevant to the political objective that Mrs. Thatcher has in mind.

Eventually, her defense secretary says, "some long- term accommodation" will be needed between the Falklands and "other countries in the area." Other officials are quoted as saying this would likely not mean transfer of sovereignty to Argentina, as the British had contemplated earlier. The islands could remain a British colony, they suggest, or become a United Nations trusteeship or receive independence.

These considerations reflect presumably the passion of the moment. They amount to a policy of casting in fresh concrete precisely the grievance which produced the Argentine invasion and then this war. This cannot be to either Britain's or the Falklanders' interest. If they win this war conclusively, or if they accept a cease-fire at some point short of total victory, the British will have political motive and moral reason to ensure that they did not fight in vain. But it could be very dangerous if the Argentines are left humiliated and determined to exact revenge, or if they fear they will be so left.

It is reassuring to learn that the United States government, which does not conceal its own interest in the matter, is doing its British ally the considerable service of speaking to it quietly about the practical advantages of restraint. The message is one the British ought to make every effort to hear over the roar of the guns.