THE ADMINISTRATION seems to have modified the strategic arms limitation proposals Secretary Vance took to Moscow last March. The position then was that Soviets could have 1) a negotiated mutual reduction in strategic nuclear arms that would include limits on the American cruise missile or 2) a treaty that merely ratified the relatively high ceilings on such weapons that the two sides agreed to in Vladivostok in 1974 - but which would defer the imposition of any limits on the development of cruise missiles (and on the Soviet Backfire bomber, which the United States had been insisting be considered a strategic weapon if our cruise missile was to be considered one).

We pen off the Backfire in parentheses becasue it isn't now and never was central to the contention. The contention concerns the U.S. cruise missile, which has become something of an obession with the Soviets. The change in the American position is that the administration is now evidently prepared to agree to some kind of temporary slowdown on the cruise without getting a substantial arms-cut agreement at the same time. As we understand the contours of the deal Mr. Vance has been alluding to - the "framework" for a SALT II agreement, which he spoke of after his talks in Geneva with Mr. Gromyko - what the United States in now willing to agree to is this: a formal treaty, running until 1985, that would incorporate numerical ceilings on strategic weapons at approximately the Vladivostok levels; an associated protocol, running for only three years, that would put some kind of limits on ground and sea launched cruise missiles, the Backfire and possibly mobile missiles; and an accompanying statement of principles, which would contain a joint commitment to seek reductions in the next SALT round.

On the basis of this skimpy outline of known and guessed at facts, it is not possible to reach any firm conclusions. But a few general observations can be made. One is that it is welcome news that the negotiations are going forward in a less show-biz mode than before - minus both the outsized delegation and the Hing Noon rhetoric that were part of that delegation's send off. Both, we calculate, contributed to the trouble in Moscow in March. Mr. Vance, a well-trained professionalism, appears to have restored an element of professionalism to the proceedings. He did not take everyone but the parlor maid with him this spilling in advance of the journey. Again, it is good news that serious political bargaining has evidently been taking place.

No one should think, however, that even without the cruise missile, Backfire and possibly some other weapons, the Vladivostok ceilings will be simple to negotiate. There are some formidable substantive matters and also matters of verification to be dealt with. And the treaty/protocol/principles formula could carry its own problems and risks. The Russians are not crazy to be so concerned with the American cruise missile: It could negate the effect of their huge investment in a better military balance (for themselves) in Europe, and it could play havoc with the strategic balance between the two superpowers. But then, so could some of the weapons now in place and coming along in the Soviet arsenal. The point is to get a good trade. What remains to be seen is whether cruise-missile development can be deferred in a way to a sound and secure strategic arms limitation nor lose the prospective benefits the technology might provide for the conventional defense of Europe. That, presumably, is also what remains to be negotiated.