Rather remarkable a change can be detected in the signals now emanating from Washington on nuclear arms control. The Reagan administration appears to be making a concerted effort to respond to concern at home and abroad that the United States may not be really committed to arms negotiations. Secretary of State Alexander Haig has assured Congress the US is serious about achieving a ''sound agreement.'' Deputy Defense Secretary Frank Carlucci made a similar call for arms reduction the other day. And now come reports that President Reagan will soon announce a formal proposal to Moscow to forgo or reduce medium-range missiles in Europe.
These are signals Americans can welcome.
Whether they mean that all the contending elements in the US administration are now agreed on the issue is uncertain. It also remains to be seen whether the administration will manage to negotiate successfully. But, when one recalls the general posture of the administration in the early months of the year - with the focus largely on military rearmament and Soviet untrustworthiness and with public expectations for arms control at low ebb - the mood appears to have shifted appreciably.
This is not surprising. There are constraints on both superpowers driving them to seek some relief from the burden of building and maintaining more and more nuclear weapons. Mr. Reagan no doubt has been sensitized to the problems confronting the Atlantic Alliance because of the antinuclear movement. But that is but one reason for a more accommodating posture on arms talks. There is also the economy. Despite putting the best face on the current recession and growing unemployment, the administration is in trouble with looming budget deficits, and one way to reduce them is to scale back on defense plans - unnecessary ones, to be sure. Mr. Reagan cannot ignore that fueling the arms race would have not only an economic but possibly a political fallout as well.
Leonid Brezhnev has his own domestic reasons for arms talks. He has just acknowledged at a meeting of the party Central Committee that the Soviet Union faces severe economic and political problems, not the least of which is a poor supply of food. Because of difficulties in agriculture and other sectors - due largely to a cumbersome, inefficient, overcentralized system - the Soviet regime has had to scale back its five-year investment plans. Significant in this connection is that it is letting its East European clients look more and more to the West for trade and credits. Poland, groping for a way out of its economic morass, and even relatively well-to-do Hungary have applied for membership in the International Monetary Fund and World Bank.
While Mr. Brezhnev has deftly been conducting a peace campaign in Europe and making political capital of awkward administration pronouncements, there is no reason to doubt his genuine concern about the arms competition. It puts an added strain on the Soviet Union's already stretched technological and manpower resources. It also heightens the dangers of war - dangers which he and millions of his compatriots have learned from bitter experience to fear.
These factors suggest that it is only a matter of time before the two sides come to some agreement. Mr. Reagan's anticipated proposals deal, of course, only with so-called theater nuclear forces or medium-range weapons. But it is hard to see how TNF talks can take place totally outside the context of negotiations on intercontinental or strategic arms as well. For one thing, a balance in TNF weapons has no significance without balanced limitations on strategic weapons. For another, the Europeans have consistently made a theater arms agreement contingent on having a SALT framework around it.
One step at a time, however. The first step is to dispel the image, right or wrong, that the Reagan presidency is lukewarm to nuclear arms control. That it now appears to be doing so is reason to be encouraged.