FOR PERHAPS THE first time since Soviet-American relations began to darken last year, the Soviet Union has come up with a statement that permits one to hope, cautiously, that Moscow may be getting the message. The statement was Pravda's commentary of June 17, made in considered reply to Jimmy Carter's Annapolis speech of June 7. The message that Mr. Carter was trying to convey at Annapolis was that while the United States is eager to seek the benefits of detente, it insists on a measure of restraint in the strategic and political competition that the two powers will continue to conduct with each other anyway. The evidence that Moscow has gotten that message is hardly conclusive. These things never are. But there are promising signs.

First, while the Pravda commentary is full of warnings along the lines that "the present course of the United States is fraught with serious dangers," it does not write off President Carter or the prospects of improved relations with his administration. On the contrary, it describes with it perceives as his new "tough line" as a "tactic," which has not yet developed "into a dangerous and uncontrollable political course," although it could. Asking rhetorically, "How will the Soviet Union respond to the toughening of American policy?" Pravda answers that Moscow "has chosen the road of peace and will not allow anyone to push it off this road.

"We do not accept the invitation to join the funeral of detente." And we don't exactly subscribe to Pravda's every word. But we do commend it for detecting a new "tough" note in American policy, for understanding that toughness is not the only element of American policy, and for wanting Americans to understand that the Soviet Union still wishes to pursue detente. That evades the question of the content of detente - but it is something.

Then, while Pravda says nothing reassuring about the pattern of Soviet (and Cuban) military moves in Africa that feeds one strain of American anxiety, it addresses the source of a second strain: Moscow's buildup of conventional and strategic arms. And here it does not merely dismiss Western concern out of hand, but rather notes, accurately, that NATO's fear is "not of today but of tomorrow, that the Soviet Union might gain military superiority in the future." To which Pravda replies: "But the U.S.S.R. and its allies have no less grounds for anxiety about the morrow, particularly in the face of the long-term programs adopted for modernizing and building up NATO's military potential."

We find that fascinating. It is a rare thing for Moscow to grant the legitimacy of American anxieties and, further, to legitimize them precisely by citing its own. For that matter, it does not happen often in Washington, either. With a rival who refuses to grant that one has grounds for apprehension, not much can be done. But that is not Moscow's pose now. It should not be Washington's.

One aspect of the Pravda commentary ought to be read attentively by those Americans who argue, or fear, that post-Vietnam, post-Watergate America cannot muster the respect of either allies or adversaries. Threaded through the Soviet commentary is evidence to the contrary. Implicitly if not explicitly, Pravda grants that the United States can launch new weapons programs, run an alliance, play the "China card" and, in general, mobilize for whatever challenges lie ahead. Far from mocking American weakness, pravda shows respect for American strength. The Kremlin does not concede any weakness or inferiority of its own. But plainly, or so it seems to us, it wants to deal.

And that is good news. A modest, useful and essential version of detente is surely within reach, if the two sides can try a little harder. From the Kremlin it will take some restraint in Africa. From the White House it will take some restraint in attacking the internal Soviet order. From the two together it will take some devotion to their main common business, control of strategic arms.