WHEN he addressed foreign ministers from a dozen Central and Eastern European nations this week, Secretary of State Warren Christopher solemnly recalled that when Czechoslovakia was threatened by Hitler in 1938 no Western democracy saw fit to help.
"The world paid the price for that dangerous short-sightedness," Mr. Christopher said in Prague on Wednesday, alluding to the consequences of appeasement - German aggression leading to World War II.
Christopher's speech was more than a history lesson. It underscored the Clinton administration's determination to stick to its plans to "enlarge" NATO to ensure that states of Central and East Europe - which fell first to Hitler and then to the Soviet Union - are permanently ensconced in the Western orbit.
Christopher's message has taken on a particular urgency. Former Communists are poised to win national elections in Russia in June, and the lower house of the Russian parliament last week voted to declare the 1991 dissolution of the Soviet Union an illegal act.
In pursuing plans to expand the Western alliance, formed in 1949 to contain the Soviet Union, the Clinton administration has gone to great lengths to assure Moscow that NATO enlargement is not designed to isolate Russia but to seize the moment to integrate a Europe long divided by cold war.
To mollify Moscow, NATO has agreed, among other things, not to station nuclear weapons for the foreseeable future in new member states. But Christopher left no doubt this week that plans to enlarge the 16-member alliance are irreversible.
"NATO's enlargement is on track, and it will happen," he said, delivering a message intended to reassure nations, including Ukraine and Georgia, that have the most to fear from the resurgence of Russian nationalism.
In their still unlikely but worst-case scenario, US policymakers see the resurgence of extremist politics and the faltering of economic-reform efforts in Russia, setting the stage for a return to the Russian and Soviet expansionism of the past.
Poland and the Czech Republic are likely to be the first two newly independent nations welcomed into NATO. But NATO officials emphasize that negotiations will be deliberate and that stiff preconditions will be required before new members are accepted.
NATO wants to move fast enough to signal to Russia, while it is still weak, that Central Europe is off limits. But it does not want to move so fast that communists and nationalists in parliament use NATO expansion as an excuse to break key arms-control agreements.
Christopher meets today in Moscow with Russian President Boris Yeltsin and Foreign Minister Yevgeny Primakov.