THE REAGAN administration has quietly paid American banks $71 million owed them by deadbeat Poland so that the banks won't declare the Poles in default. This is the first payment on loans that the Agriculture Department made or guaranteed to finance grain exports. For making it, the administration has come under hot attack for bailing out the repressive Polish regime, not to speak of the Kremlin regime behind it.

The critics have a right to object. It is offensive to see the United States government lifting from the Polish government, however temporarily, an obligation it freely assumed and a burden that, morally speaking, it and its Soviet partner ought to be compelled to bear. The contrast between the administration's loud public calls for pressure and its quiet provision of temporary relief is painful. Mr. Reagan's aroused supporters would be untrue to their faith in their man if they weren't boiling mad.

Mr. Reagan, however, appears to know something that they don't know--unless you subscribe to the tired and patronizing theory that this is another of those decisions his advisers made while he napped. He appears to know that a decision to force Poland into default would yield an immediate political satisfaction, but would also inflict potentially devastating damage on the West's banks and trade-- especially on West Europe's banks. At last month's meeting of NATO foreign ministers, the United States got its allies to agree to act--that is, to act together--on the Polish debt. Forcing a default unilaterally would mean the administration was breaking that common front, with all the considerable complications that would come in tow.

It would be different if the United States lived in isolation so far as friends and obligations are concerned. In those conditions, in which it was taking upon itself the full consequences of its actions, it could match a policy to the outrage that the administration and so many American citizens feel over the continuing assault on Poland. But when the consequences of its actions fall more severely on others than on itself, as they unquestionably would in the event of a Polish default, then a measure of restraint is unavoidable, and even statesmanlike. The diplomacy of debt requires a discipline of its own.