A haunting warning came this week from George F. Kennan, 79 now--a driven, concentrated man of an increasingly spectral appearance--whose contributions to diplomacy, history and the public dialogue entitle him as much as anyone to be heard out on the subject of relations with Russia.

He was careful not to say he expected the outbreak of war. But he did state that civility and privacy of communication between the two great powers had largely broken down, that their statements and actions were now "permeated with antagonism, suspicion and cynicism," that public discussion of theirrrelationship had become almost "totally militarized, in this country at least," and that these are "the familiar characteristics, the unfailing characteristics, of a march toward war--that and nothing else."

For all of its emotion and imbalance, it was a riveting statement, bound to echo around the world. Certainly it expressed the full measure of the darkest anxieties felt about Ronald Reagan personally by his audience, the American Committee on East-West Accord, and by many other people elsewhere.

In his sweep across the current bleakness, Kennan said little about the things blurring his picture: that the arms control talks are stuck but continue, that new grain talks are opening, that Reagan is under strong international and domestic pressures--pressures received with some understanding by some of his leading aides--to moderate the whole range of his East-West policies. The day Kennan spoke, for instance, Reagan patiently explained why one cannot charge the Kremlin with arms treaty violations without good evidence.

But Kennan did go to the intellectual source of some of Reagan's most extreme public statements, the view that Soviet- American tensions flow "automatically from the nature of the Soviet regime" and are therefore unavoidable. From "this allegedly unbounded and unquenchable thirst for power" on the part of the Soviets, Kennan observed, comes the conclusion that there is "no language they could be expected to understand, other than that of intimidation by superior military force." He pronounced this image "grotesquely overdrawn . . . inexcusably childish, unworthy of people charged with the responsibility for conducting the affairs of a great power in an endangered world."

Kennan addressed in passing the particular Soviet policies which, as he put it, "grate severely on Western sensibilities." Characteristically, he attributed these policies not to political choice but to historical or cultural inheritance: "a high general sense of insecurity, a positively neurotic passion for secrecy, a marked sensitivity to conditions in border regions and a tendening negotiating positions desicy to overdo in the cultivation of armed force." But, he said, these features are familiar, less acute than they used to be, and finally counterbalanced by the Kremlin's "serious and primary interest" in avoiding a major war.

As for what he called the question of "human rights," he presented a choice between "suddenly grafting democracy onto an unprepared people from outside" and pursuing world peace. At this point alone his audience interrupted him with applause.

Kennan's views, ever elegantly articulated, have long been stirring his listeners and readers to various blends of apoplexy and delight. No matter; he has the enviable quality of focusing always on things that matter deeply to other people. Never scholastic, he goes unerringly to the place where political ideas and people's feelings, not least his own, intersect.

In the current circumstances, he speaks with the authority of someone who has not only seen and studied much but has made and confirmed his final choices. There is an old man's economy of truth in his emphasis on the danger of nuclear war and on the requirement to restore to Soviet-American relations "a chance to breathe."

But it is not so much for policy analysis, always arguable, that one turns now to George Kennan. It is for glimpses of an uncommon, even mystical prophetic power: "At the end of our present path of unlimited military confrontation lies no visible destination but failure and horror. There are no alternatives to this path that would not be preferable to it. What is needed here is only the will--the courage, the boldness, the affirmation of life-- to break out of the evil spell that has been cast upon us, to declare our independence of the nightmares of nuclear danger, and to turn our minds and hearts to better things."