WHEN Bill Clinton travels to Russia today, he'll have a major task on his hands: convincing Russian President Boris Yeltsin that the idea of expanding the NATO alliance into central Europe is a sound idea.
When he returns home he'll have another major task: convincing Americans of the same thing.
Although they disagree on timing, Clinton administration officials and an apparent majority in Congress are in favor of enlarging the Western military alliance, which was established in 1949 to contain Soviet expansion in Europe.
But opposition exists among some foreign-policy elites who worry that expanding NATO to include former Soviet Bloc countries such as Poland, Hungary, and the Czech Republic could alienate Moscow and strengthen reactionary forces in Russia.
As for US public opinion, it is contradictory: A majority favors enlarging NATO, but a majority also opposes using US troops to protect the new countries that would be brought under NATO's protective umbrella, according to polls.
''There are very serious domestic hurdles that need to be addressed,'' says Charles Kupchan, author of a report on NATO recently issued by the New York-based Council on Foreign Relations.
''Not once has anyone talked about how much it's going to cost or whether Americans are prepared to put their lives on the line -- that's what this debate is all about,'' adds Mr. Kupchan.
During his visit to Russia to commemorate the end of World War II, Mr. Clinton will attempt to convince Mr. Yeltsin that the motive behind enlarging NATO is not to isolate Russia but to seize the moment to reintegrate a Europe long divided by cold war.
Implicit in Clinton's message is that an expanded NATO will minimize the possibility of resuming the historic Russian-Germany rivalry over central Europe.
The Clinton administration is exploring several options to mollify Yelstin. These include assuring him that an expanded NATO would not install nuclear weapons in former East bloc nations and that Washington has no objection in principle to Russia becoming a full NATO member.
Though diplomats have been furiously preparing the details of these assurances, it is still unclear whether Clinton will invoke them in talks with Yeltsin.
How fast to expand?
For most US policymakers, the issue is not whether but how fast the Western military alliance should be enlarged.
The argument for rapid expansion is that it would quickly remove ambiguity about the future of central Europe, sending an unmistakable signal to Russia, while it is still weak, that the region is forever off limits.
If NATO does not expand now, rapid expansionists insist, it will languish because it will become irrelevant to the new security challenges that face Europe.
Opponents say rapid expansion will alienate Russia, possibly prompting Moscow to break arms control agreements or, in the worst case, reassert control over former Soviet states like Ukraine.
Advocates of slow expansion -- or no expansion -- say the US needs to base its policy on actual Russian behavior and not on the automatic assumption that Russia will once again be an expansionist power. That means treating Russia after the cold war like the European powers treated France after the Napoleonic wars and Germany after World War II: ''Integrate if possible, isolate only if necessary,'' Mr. Kupchan says.
European past and present
The debate over NATO expansion raises fundamental questions of what Europe is. For 50 years, the continent was divided politically because of where the Soviet army happened to be at the end of World War II -- that is, in most of central and Eastern Europe, which was subsequently isolated behind the Iron Curtain.
But culturally and politically, countries like Poland and Hungary -- among the likeliest early NATO entrants -- have long been part of Europe. This is one reason for the push to expand NATO -- and political institutions in Europe, like the European Union -- eastward.
''The Europe of the institutions should gradually and inexorably expand to match the Europe of the map,'' US assistant secretary of state Richard Holbrooke says.
But expansion could require NATO, already burned by the Bosnia crisis, to deal with new ethnic tensions, like those created by the presence of a half-million Hungarians in Slovakia. It is just such complications that concern opponents of rapid expansion, who worry about extending security guarantees to weaker and potentially less stable states.
''How in the world can you strengthen a military organization that is important to American national interests by adding weaker states and expanding its responsibilities?,'' asks Alton Frye of the Council on Foreign Relations.
As for Russia, once a member of the ''concert'' of Europe, it has not been an integral part of political Europe since the Bolshevik Revolution of 1917.
Proponents of rapid and slow expansion alike are sensitive to Russia's concerns over the future of NATO. Moscow has had second thoughts about joining the ''Partnership for Peace,'' a group of former Soviet bloc states that have agreed to military and political cooperation with NATO.
Even as NATO consults with prospective new members, says former national security advisor Zbigniew Brzezinksi, an advocate of rapid enlargement, it should reassure Moscow that NATO expansion is not directed against Russia. To assuage Russia's concerns NATO could agree to ban forward deployment of US or German troops or nuclear weapons, Dr. Brzezinksi says.
''The best way to deal with Russia is not to isolate or antagonize Moscow,'' says the Council's report on NATO. ''Rather it is to bind the emerging democracies of Central Europe to the West even as the West reaches out to forge a new cooperative relationship with Russia.''
The debate over timing could be muted by procedural issues. The requisite consultations within NATO over terms and conditions of admittance all but guarantee a slow expansion.
''There's no danger that it will go so fast that it could be viewed as provocative or insensitive to legitimate Russian concerns,'' says Brzezinksi.