It seems to be fairly clear from the record that President Reagan did not understand until it was too late how strongly the Western allies feel about his efforts to stop them from building a gas pipeline from Siberia to Western Europe.
It is reported that when British Prime Minister Margaret Thatcher was in Washington on June 23 she told him exactly how she and her Parliament felt on the subject and he replied that he had thought that she ''could live with that.''
Well. On June 30 the British Board of Trade invoked a Protection of Trading Interests Act under which companies doing business in the United Kingdom can be compelled to inform the British government of any requirements placed on their activities by an outside government. In effect, subsidiaries or licensees of an American company must disclose limitations placed by President Reagan on those companies in Britain which are under contract to sell parts or equipment for building the controversial pipeline.
On the following day Mrs. Thatcher stood up in Parliament and declared:
''The question is whether one very powerful nation can prevent existing contracts from being fulfilled. I think it is wrong to do that.''
Under British law the subsidiaries or licensees of United States companies in Britain can be forced to defy President Reagan's pipeline ban and fulfill their existing contracts.
The British government has not yet actually ordered those companies in Britain to go ahead with the contracts in spite of the Reagan ban. But the indications are that the West Germans, the French, and the British all intend to go ahead with the pipeline in defiance of the American President.
In the meantime, Mrs. Thatcher's open defiance of the President on this point stands as the first major breach between the two countries since Mr. Reagan became President. Until Mrs. Thatcher's statement to the House of Commons on July 1, she had given Mr. Reagan more enthusiastic and public support than any other head of government in the alliance. Her policy had been to act and talk as ''the most loyal ally.'' Mr. Reagan could count on her support.
The issue at stake here is the importance of the alliance itself. Economic sanctions against the Soviet Union might have some impact on the Soviets and on their policies if they were applied and implemented by all members of the NATO alliance and by all other associates of the US in other parts of the world.
The attempted ban on the pipeline, and on Japanese oil drilling for the Soviets off Sakhalin, might actually mean something if the entire US system of alliances and association acted in unison.
But if and when the US acts alone and its allies and associates proceed in spite of US wishes - the sanctions merely delight the Soviets because they become an element of discord inside the alliance. They expose weakness in the alliance. They do not prevent the Soviets from getting the pipeline, or from expecting a substantial income in hard currency from sale of the gas when the pipeline is finished.
The alliance is not yet in decisive dissolution. This is only a case where Mr. Reagan has had to learn the hard way that the allies cannot be coerced, or even led, in a direction contrary to what they conceive to be in their own best interests.
But it does seem to expose a lack of awareness of how important the alliance is to the US.
Let us just take one superficial way of measuring the matter. The US has today slightly over 2 million men and women in its armed forces. The Soviet Union has approximately 3.7 million - not quite twice as many. But the armed strength of the major Western allies - Britain, France, West Germany, and Italy - adds an extra 1.7 million. The smaller allies - Belgium, the Netherlands, Denmark, Norway, Portugal, Greece, and Turkey - contribute another million.
The Western alliance can field armed forces of almost 5 million.
And if the US maintains effective good relations with both Japan and China on the other side of the world - the US and its friends can outnumber the Soviets massively.
Current debates over the defense budget in the Congress in Washington show that it would be difficult indeed to match the Soviets in US military manpower alone. Congress is balking even at a modest Reagan proposal for an additional 36 ,000 American military people. The US alone simply cannot out-man the Soviets. The US with its friends and allies can. The more dangerous the Soviet Union is conceived to be, the more important is the alliance to the US.
Sanctions which do not command alliance cooperation help the Soviets by weakening the alliance.