AT ITS summit over the weekend, the European Union tried to learn the lessons of the Kosovo conflict. It approved a Franco-British plan to develop a rapid-deployment capability, so that Europe will rely less on America in future Kosovo-type conflicts. And it invited seven countries--the largest among them being Turkey--to begin the process of admission to the EU. This second move is intended to extend prosperity and hence stability eastward, and so make more Kosovos less likely.

For a variety of reasons, the EU has been slow to respond to this decade's challenges in the eastern half of the continent. When communism collapsed, Germany's energy was consumed by the absorption of former East Germany; Britain descended into a period of drift following the departure of Margaret Thatcher; and France was more interested in political and monetary union within the existing EU than in reaching out to easterners. As a result, the European Union still has not admitted any ex-communist country, whereas Poland, Hungary and the Czech Republic have been welcomed into NATO.

Fortunately, the EU now seems less introspective. The project of monetary union, which consumed EU energies for much of this decade, is now largely done: A European Central Bank sets interest rates for the 11 nations that have given up their currencies in favor of the euro. Equally, Germany is recovering from the effort of reunification, and Britain has exchanged post-Thatcher drift for the vigorous leadership of Tony Blair. Moreover, the war in Kosovo has taught the leaders of the EU that their prestige depends on their ability to respond to instability in their neighborhood.

The challenge now is to sustain the momentum of the summit. The rapid-deployment capability is supposed to be ready by 2003; getting there will take a commitment to modernize force structure and reverse cuts in defense spending. Equally, Turkey's accession to the EU may still be years or even decades away; and even countries such as Poland and Hungary, which started the accession process two years ago, are being made to wait until 2004 or so. In all, a dozen suitors are on hold, from the Baltics to the Balkans.

The EU needs to reform its bureaucratic machinery in order to cope with expanded membership. Despite that legitimate reason for delay, it is dangerous to keep suitors waiting. If the momentum of democratic and economic reform in Eastern Europe is not sustained, old authoritarian habits may reassert themselves: Look at the reversal of reform in Russia. Now that the EU's leaders are headed down the right path, they need to exude more urgency.