PROGRESS ACHIEVED by the executive branch in dealing with both China and the Soviet Union brings to center stage a question in which the Congress has the leading role: bestowing the normal trade and tariff conditions misnamed "most-favored-nation" (MFN) status upon the two communist powers. With Peking, the MFN question arises as the result of governmental agreement on a basic framework for trade. With Moscow, it arises in the context of the expected imminent conclusion of a SALT agreement and the scheduling of a summit in June.

Five years ago, with Soviet Jews foremost in mind, Congress made a good record on emigration a condition of normal trade with all communist countries. Some legislators did this solely out of a concern for emigration. Others saw emigration as a way to control trade and restrain detente. The Soviet Union now meets a fair emigration test-Jews are departing at the rate of 4,000 a month. Though this is accepted by Rep. Charles Vanik, one of two leading drafters of the trade-emigration link, the other, Sen. Henry Jackson, stands fast.Mr. Jackson further confounds the administration by suggesting that an imbalance be deliberately created by offering MFN to Peking alone. The administration is puzzling over how to proceed.

MFN should be offered simultaneously and soon to Moscow and Peking. To favor Peking alone would be to risk offending the Kremlin for no useful purpose. The technical reason to extend MFN to both is that their emigration policies meet the standards of the law. The economic reason is to make money. The political reason is that MFN can help broaden the limited areas of common interest the United States has with the two countries. It seems unlikely that, as some in the administration desire, Congress will repeal Jackson-Vanik. But repeal is not vital. The president can waive the trade restrictions if he receives adequate emigration "assurances." In deciding what constitutes "assurances," he should seek a formula that keeps the Kremlin interested in allowing a reasonable flow but does not bestow a free pass. He should have such a formula ready for summit bargaining.

The "Jackson amendment" has provoked endless debate over the ends and means of American foreign policy. The debate is over. Whatever else the amendment has accomplished, it can now be said to be responsible for a considerable level of emigration. Almost any other politician would be eager to claim a success. Scoop Jackson, still bargaining, hangs back. His resistance should be smothered in praise.