AT LAST the world's industrial posers have agreed on action to protect themselves from continual oil-price increases and disruptions. Until now they have mainly confined themselves to standing around baa-ing apprehensively like a flock of sheep waiting to be sheared. But on Friday, the 21 nations that use two-thirds of the world's oil said that, together, they would cut their oil consumption by 5 percent.

That is an important and useful response. It would balance the reduction in supply that the Iranian revolution has caused. But a great deal depends on the United States and whether it takes this commitment seriously. In a country that uses 20 million barrels of oil a day, a 5 percent reduction is hardly drastic. But it is going to require more than trpid appeals from the White House for voluntary conservation. Merely shutting filling stateions on Sundays won't be enough.

Following the oil crisis in 1973-74, most other countries took steps at least to keep their oil imports from rising. The one glaring exception was the United States. It kept buying more and more, heedless of rising prices and reckless of risks. Will the U.S. government now move rapidly and effectively to cut oil imports? Or will it fall into another desultory quarrel over how to do it?

The energy crisis in this country is essentially a crisis of political purpose and trust. Every attempt at energy policy gets dissolved in public suspicion of the oil companies and hostility toward them. It is quite true that the oil compaines are making money this winter. Anyone with large inventories, trading in a tight and rising market, can hardly help making money. It is also true that by protecting their inventories, not to say grabbing and hoarding, the companies are making mattes worse. A great many Americans conclude that, since the oil compaines progit from the shortage, they must have engineered it.Certainly it is easier and more satisfying to believe in corporate conspiracies than to consider other possible causes, such as the behavior of consumers or the increasing inclination among OPEC nations to conserve their resources.

A few days ago, Rep. Albert (D-Tenn.) triumphantly produced a study, done for him by the Congressional Research Service, suggesting that the whole shortage was a fake. The paper points out that world oil production now is very little lower than in the first nine months of last year. The Department of Energy immediately replied that those figures are misleading. Early 1978 was an abnormal period; the industry had overshot in building inventories and was holding down purchases while it worked off excessive stocks. Meanwhile, world demand for oil has been steadily rising. There's now a real gap, the Energy Department concludes, between available supply and the amount of oil that the world expected to use this winter.

Whom to believe? The conspiracy theories are always more fun. Another advantage is that they don't threaten those weekend drives to the shore.

In making up your mind, you might want to consider that unprecedented cutback agreement on Friday by the 21 governments. Some of them, notably the British and the French, have very competent intelligence resources of their own. Several have diret access to the industry through government-owned compaines that operate on an international scale. Cutting back on oil imposes a certain economic cost on a country. It's hard to think that the French, British, Germans, Swedes and Japanese would do it without some substantial reason. Evidently they do not take Mr. Gore's charge seriously. Evidently they conclude that the shortage is real, and that it is dangerout. They are right.