One of the most surprising consequences of current American involvement in the Middle East is the reappearance of a kind of conservative isolationism we have not seen in a long time. It would not have been a surprise if we had witnessed a resurgence of left-wing isolationism, nourished on memories of the Vietnam War. That may yet come, but for the moment one sees even Jesse Jackson supporting the use of American troops to resist Iraqi domination of the Persian Gulf. Among conservatives, however, an articulate, dissident minority is questioning whether it is in the American interest to intervene, at the risk of war, to protect our friendly states in the Gulf -- along, of course, with the world's oil supply.

That conservatives should conceive of American foreign policy in terms of our "national interest" rather than in general, undifferential terms of abstract principles is quite appropriate. The term itself, "national interest," with its nationalist overtones, fits quite comfortably into the conservative lexicon. Liberals and those on the Left tend to avoid the term, relying instead on a "universalist" vocabulary (e.g., "world order," "world peace," etc.). But to insist that "national interest" be the lodestar of American foreign policy is one thing; to define it in particular circumstances is another. I have the strong impression that some American conservatives are not very good at making the transition, largely because they are inclined to a narrow, isolationist view of our "national interest."

The United States is a world power -- at the moment the only world power. There is no way any kind of traditional isolationism can serve us as a useful guide to policy. That doesn't mean we are, automatically and everywhere, the world's policeman. But it does mean we have to be ready to perform a policing role when, in our judgment, it is in our national interest to do so. Our current response to the Iraqi invasion of Kuwait seems to me to be clearly in our national interest. Even if the U.N. had disapproved and our allies were less supportive, I still think it would be in our national interest to intervene.

The reason is simple: it is a serious challenge to our national interest to have any single, hostile power control the Middle East's reserves and supply of oil. It is for this reason that we assisted a weaker Iraq in its war against a stronger Iran -- even though it was Iraq that had irresponsibly ignited the war. And it is for the same reason that we are intervening to ensure the freedom of Saudi Arabia and the Trucial States from domination by a resurgent Iraq. The balance of power in the Middle East is as critical for the United States as the European balance of power was critical for Britain throughout the 19th century -- and it didn't really matter if that balance was threatened by Napoleon's France or the kaiser's Germany.

But why, conservative isolationists are asking, is it so critical for us? After all, we import only 50 percent of our oil, whereas Germany, France and Japan are totally dependent on oil imports. Why aren't they doing the job in the Middle East?

The answer to this is twofold. First, they lack the military resources and political will to play any such role. Second, it is not so clear that it is in our national interest for them to do so. Would we really feel relieved if the Japanese navy were patrolling the Gulf while 100,000 Japanese soldiers landed in Saudi Arabia? I very much doubt it.

Besides, the statistic on dependency for imported oil is beside the point. It is the price of this oil that counts. If Iraq were to dominate and control Gulf oil production, and therewith dominate and control OPEC, the price of oil would -- as the Iraqis have promised -- go up. True, the United States could experiment with a dual price for oil, regulating and price-fixing domestic production. Such experiments have been tried in other countries and end up being strangled by red tape. Oil is oil, and you cannot tell its national origin by looking at it.

But it wouldn't matter even if you could. If the economies of Western Europe and Japan are depressed by an increase in the price of oil, our economy will be depressed as well. We are part of an integrated international economy, and our prosperity is as much at risk as theirs. An Iraqi-dominated OPEC means a depressed -- perhaps very depressed -- American economy. Is it in our national interest to tolerate that?

"Ah," some conservative economist is bound to retort, "you assume that OPEC and its fellow-travelers will remain an effective cartel. But we know that cartels eventually collapse as individual members begin to cheat." Yes, they do -- eventually. How many years before "eventually" comes into force? Our economist has no reply to this noneconomic question.

It is a puzzle that conservatives should be so indifferent to Iraqi military hegemony in the Gulf, with its obviously damaging consequences to the well-being of the United States and its trading partners. They seem to have allowed a born-again isolationist impulse to overwhelm all the obvious considerations of our national interest that are now at stake in the Middle East. Nor are these considerations narrowly economic. A dominant, belligerent anti-Western Iraq, which in a few years will have a nuclear warfare, chemical warfare and biological warfare capability -- surely that is a specter that were better laid to rest now rather than, at much greater cost, later.

The writer is editor of The Public Interest.