THE SOVIET government's charge - at once denied - that American intelligence agencies framed and coerced the Soviet U.N. official who has just defected in New York has to be understood for the pretense it is. The Kremlin goes to prodigious lengths to prevent defections among the handful of its citizens it permits abroad, and it simply doesn't wish to acknowledge that any of them would voluntarily relinquish the privileges of Soviet citizenship. Nothing more is at stake in its protest than pride and propaganda - and the prevention of the next defection.

We relize that the Soviet's American lawyer describes his client's act not as a defection but simply as a personal decision not to go back to Moscow as ordered. That strikes us, however, as a procedure meant to keep the act from disturbing Soviet-American relations. The man himself, Arkady Shevchenko, is a rare catch, perhaps all the more satisfying for being a walk-in windfall - unless he is a double agent who had previously been working for Western intelligence and is now coming in from the cold. An under-secretary, he was the ranking Soviet in the U.N. Secretariat. His long, high-level diplomatic experience and his special expertise in arms control put him in a position to tell American officials a good deal, if he chooses to accept (if he hasn't already) the usual asylum-for-information exchange.

Oddly, Mr. Shevchenko's move raised fears in some American quarters that it would spill over adversely on general Soviet-American relations. It was, one American was quoted as saying, "the last thing we needed at this time." How absurd.The professionals who make Soviet policy surely will not let an isolated incident, one of the hazards of East-West life, get in the way of other matters. If we are right in our surmise about the way it is being handled, then American policymakers are determined not to let that happen either. There is no need to gloat: Some you win, some you lose. But no American need feel apologetic to the Soviets for the embarrassment one of their own citizens has caused them. It is only necessary, discreetly, to welcome Mr. Shevchenko.