When so many have contributed so much to the general confusion over U.S. purposes in the Persian Gulf, it may be unfair to single out Defense Secretary Weinberger's TV talk-show dispatches from the ''tanker-war'' front. And yet they seem to me to capture, as nothing else has, the essence of what is so foolhardy about the way the administration has caught the U.S. Navy up in the Gulf and caught itself up in a no-win clash with Congress over the proper way to share the so-called war powers.

''When you talk with the sailors and the airmen and the soldiers and the others who are out here,'' Weinberger reported from Bahrain, ''you get quite a different perspective than when you listen to a lot of sterile debate about philosophic concepts, or whether or not somebody is being notified.

''You are in a very real world out here, and we are doing things that are essential to maintain the freedom of the seas . . . and the freedom of important cargoes to be shipped through international waters. That's what we are doing . . . and we are doing it under the direction of the president.''

Well, that's clear enough; congressional dissenters should sit down and shut up. The Senate had defeated an effort to invoke the War Powers Act, which would require congressional approval for deployment of U.S. forces under conditions of ''imminent hostilities'' for more than 90 days, and Weinberger was ''a little puzzled.'' What Congress was now talking about is ''something worse,'' he argued: a proposal that would allow the United States to maintain a naval presence in the Gulf but require congressional approval within 90 days for the U.S. ''reflagging'' and escorting of 11 Kuwaiti tankers.

''So what in the world would we do?'' Weinberger asked. ''It is, I think, the height of absurdity.''

Now, that's less clear. If Weinberger really wants to know what the United States could then do, the answer is that it could do what it did to that Iranian mine-layer the other day, for one thing. It could also do pretty much what it did for the first three years or more of the tanker war with a much more modest U.S. naval presence. During those years, the periodic flare-ups of the tanker war did no serious violence to freedom of navigation in the Gulf. Still less did Iranian attacks on Persian Gulf shipping present any unique threat to Kuwaiti-owned tankers.

On this point, the records of Lloyds of London are instructive. In the 18 months from January 1986 to June 1987, Lloyds lists some 70 Iranian attacks, of which only four involved Kuwaiti-owned tankers; only one did significant damage. No ships carrying the American flag were hit. While American-owned ships under foreign registry were attacked, no U.S. convoy service was offered to those vessels. Only 28 of the 70 vessels attacked were actually bound for Kuwait, and most of the targets suffered only minor damage or none at all.

If the administration wants to argue on geopolitical grounds that it had to ''reflag'' the Kuwaiti ships because Kuwait has whipsawed us with a threat to turn to the Soviets, that's one thing. (It's difficult, however, to sustain the argument that the U.S.-Soviet balance of power in the Persian Gulf was really at stake.) If it chooses to argue that it wanted to help an ally of Iraq, by way of encouraging Iran to accept a diplomatic solution to the long and bloody Iraq-Iran war, that might be defensible as well.

But when Weinberger now says that Iranian mining of international waters is ''about as hostile an act as you can imagine'' and that the defense of ''freedom of navigation'' for all shipping against this threat is now ''the principal American purpose to be'' in the Persian Gulf, he is in a poor position to be talking about ''absurdity'' -- not to mention insisting that hostilities are not ''imminent'' by any reasonable definition of that word.

By its stubborn, semantic refusal to obey a law that it doesn't like, on the grounds that it is unconstitutional, the administration has, as a practical matter, carried us well past the point when the letter of the War Powers Act can be invoked. But its spirit is very much alive in Congress. There will be repeated efforts, even in the face of White House veto threats, to bring Congress into the policy-making process.

And Weinberger should be the first to welcome them. Three years ago, in a speech to the National Press Club, the secretary offered some tests to be applied ''before the United States commits combat forces abroad.'' Among them was ''some reasonable assurance that we will have the support of the American people and their elected representatives in Congress.''

If things do not take a bad turn in the Persian Gulf, there is, I suppose, nothing to worry about. But Weinberger's own experience with the war-powers issue in Lebanon in 1983 ought to be reason enough for him to apply his own sensible, post-Lebanon test to the Persian Gulf.