His voice is a bit frail now, but the mind, even at age 94, is as sharp as ever. So when I reached George Kennan by phone to get his reaction to the Senate's ratification of NATO expansion it was no surprise to find that the man who was the architect of America's successful containment of the Soviet Union and one of the great American statesmen of the 20th century was ready with an answer.

''I think it is the beginning of a new cold war,'' said Mr. Kennan from his Princeton home. ''I think the Russians will gradually react quite adversely and it will affect their policies. I think it is a tragic mistake. There was no reason for this whatsoever. No one was threatening anybody else. This expansion would make the Founding Fathers of this country turn over in their graves. We have signed up to protect a whole series of countries, even though we have neither the resources nor the intention to do so in any serious way. [NATO expansion] was simply a light-hearted action by a Senate that has no real interest in foreign affairs.''

''What bothers me is how superficial and ill informed the whole Senate debate was,'' added Mr. Kennan, who was present at the creation of NATO and whose anonymous 1947 article in the journal Foreign Affairs, signed ''X,'' defined America's cold-war containment policy for 40 years. ''I was particularly bothered by the references to Russia as a country dying to attack Western Europe. Don't people understand? Our differences in the cold war were with the Soviet Communist regime. And now we are turning our backs on the very people who mounted the greatest bloodless revolution in history to remove that Soviet regime.

''And Russia's democracy is as far advanced, if not farther, as any of these countries we've just signed up to defend from Russia,'' said Mr. Kennan, who joined the State Department in 1926 and was U.S. Ambassador to Moscow in 1952. ''It shows so little understanding of Russian history and Soviet history. Of course there is going to be a bad reaction from Russia, and then [the NATO expanders] will say that we always told you that is how the Russians are -- but this is just wrong.''