WASHINGTON -- Just as the United States removes the final obstacles to expanding NATO, a chorus of skeptics are asking, "Why the rush?"
On Capitol Hill and in think tanks, the topic that for years caused heads to nod and eyes to glaze -- the future of the U.S.-led North Atlantic Treaty Organization after the Cold War -- has suddenly seized attention.
Sen. John W. Warner, a Virginia Republican, warned the Clinton administration recently that American taxpayers would not foot the bill for NATO expansion.
Sen. Edward M. Kennedy, a Massachusetts Democrat, called the effort a misplaced priority, far less important than preventing the former Soviet Union's nuclear arsenal from falling into dangerous hands.
The Federation of American Scientists, a research organization that specializes in security issues, calls expansion "both unnecessary and unwise."
Yet the administration, having won over its European allies to the idea of expanding NATO, is close to gaining the once-unthinkable: Russian acquiescence.
An enlarged NATO is expected to exclude Russia while absorbing several nations formerly controlled by Moscow.
The administration says its overarching goal is a peaceful Europe, with nations once caught between two superpowers now anchored to the West and with a democratic Russia in a partnership with former adversaries.
It also sees in NATO expansion the best insurance against any effort by a resurgent Russia to dominate its neighbors. Backing off now, officials argue, would disappoint prospective members and display a lack of Western resolve.
Secretary of State Madeleine K. Albright left yesterday for Moscow, where she will meet today with Foreign Minister Yevgeny M. Primakov in a bid to advance an agreement between Russia and NATO that would spell out their future relationship.
Negotiations have become tangled by Russian demands for explicit guarantees that NATO won't put troops or nuclear weapons closer to Russian borders.
This pact will likely be signed at the end of May in Paris, handing the Clinton administration a foreign-policy triumph and finally consigning Russia's five-decade military standoff with NATO to history.
Within two months, NATO is set to invite the first new members -- probably Poland, Hungary and the Czech Republic -- and to open the door to further expansion.
That action will culminate a Clinton administration policy evolution from initial reluctance to expand NATO, through a period of internal debate and halfway measures called the Partnership for Peace, and finally to an all-out push for expansion.
It will also complete a personal odyssey for the administration's point man in the effort, Deputy Secretary of State Strobe Talbott, who evolved from skeptic to full-throated supporter of expansion and went to work convincing Russia that NATO posed no threat.
The effort was spurred in part by lobbying led by Americans of Eastern and Central European ancestry who were determined to prevent "another Yalta" -- the World War II agreement between the allies and Stalin that pushed Eastern Europe into the Soviet sphere of influence.
The rush to NATO expansion, however, has left unanswered the most fundamental questions about the consequences.
"There is widespread unease about this," says Michael Mandelbaum, a professor at the Johns Hopkins University's School of Advanced International Studies. A harsh critic of NATO expansion, Mandelbaum fears it would undermine democratic reform in Russia by generating support for anti-Western hard-liners.
"If you polled the foreign policy community, I bet the vote would be 3- or 4-to-1 against."
Still uncertain is which countries will be admitted, why some will be let in and not others, how long the process will take and what it will cost.
This most profound change since the world's mightiest alliance was founded five decades ago could affect every American service member and taxpayer.
"When America expands its nuclear umbrella over new countries, and when NATO moves its defense perimeter near the territory of our former adversary, it's a big deal," retired Sen. Sam Nunn, a Georgia Democrat who is a skeptic about NATO expansion, said a recent speech.
It is widely assumed that Poland, the Czech Republic and Hungary will be the first countries added to NATO, probably by 1999. But their path to membership isn't totally clear: Poland only recently brought its military under civilian control, and Hungary spends far less on defense than NATO will demand.
As for whether Eastern European countries are ready to mesh forces with the alliance, "some are closer than others; none are there yet," says Jeffrey Simon, a senior fellow at the National Defense University and author of a book on NATO expansion.
He adds: "It's absolutely essential that the first group be successful. If you have a failure, you're not going to have a second group."
Belatedly, France is roiling the waters by sponsoring its ally Romania as an early entrant. Italy, meanwhile, is backing Slovenia.