NO DOUBT the administration could put a crimp in the Soviet gas pipeline. If it could not altogether block it, it surely could delay and raise the cost of this $25 billion project to carry natural gas from Siberia to Western Europe. This is the largest East-West deal so far contemplated, and it is central to Soviet energy and hard-currency requirements in the late 1980s and in the 1990s. For the United States to do in the deal, as it is still considering trying to do, would unquestionably make the administration's point that the Soviet Union should be required to pay heavily for the repression in Poland.

Unfortunately, this is not the whole of it. It may not be the half of it. Some other hard realities must be cranked into any pipeline decision, and when they are, it is clear that for spoiling it the United States might pay even more heavily in its way than the Soviet Union would pay if the deal were spoiled.

"It boils down," one official told The Post's Dan Morgan, "to weighing the damage to the Soviet Union against damage to the alliance." Precisely so. For the Europeans consider the deal already made. Not unfairly, they regard any American inclination to reopen it unilaterally as harassment of a sort unworthy of their leading ally. For some years they have been warned by successive American administrations against becoming excessively and dangerously reliant on Soviet energy. Yet the United States has been unable to assure them of adequate alternative supplies, in the event that they could not purchase Soviet gas.

The gas would not be pumped for some years. Meanwhile, there are the jobs to be provided from making the pumps and the pipes and the rest of it. The recession is hurting in Europe, and the economic benefits of the pipeline would be immediate. Moreover, even if the United States did decide to move against European companies planning to produce pipeline equipment under license from U.S. firms--and this is the favored approach--other ways would doubtless be found to produce that equipment. The technology is simply not all that esoteric. Can you imagine, by the way, the reaction that would follow application of one of the sanctions that the administration is said to be weighing--the arrest of an officer of one of the offending European companies who had flown into Dulles or JFK?

We leave to last the matter that is, for excellent reason, first on almost every European's lips. Is it not yet clear to this administration that, by continuing to sell massive amounts of grain to the Soviet Union, the United States loses any serious claim to ask for painful sacrifices from its European allies? In contrast to a pipeline cutoff, a grain cutoff would have not just a political and symbolic effect but also an immediate and real impact on the Soviet Union. It would bring home in a fashion that no other sanction can the West's disapproval of what the Soviets have done in Poland. Yet Mr. Reagan holds back, citing a campaign promise.

At this point in the discussion, one can hear from not far offstage a host of mutterings about the sapping of the will of the West, the inability of the democracies to coordinate policy in their own defense, the readiness of capitalists to sell their adversaries the rope for their own hanging, and so on. These are not insubstantial complaints. They go to structural as well as political flaws in the alliance. They require the continuing attention of serious people.

Unless the United States really means to go it alone, however, it cannot respond to these difficulties in a manner that makes it all the harder for the allies to be brought along on this and other matters. This would be the likely effect of an American decision, taken over the Europeans' protests, to cut a pipeline intended to provide their gas. Certainly the United States cannot so respond without first deciding, very carefully, that it is not worth it even to try to bring the allies along. If the Reagan administration means what it says about the continued validity of the Atlantic alliance--and we think it does--it must act on the basis of that fundamental fact, not simply on the basis of its frustration.