TODAY'S SUMMIT in Helsinki, convened to boost European defense cooperation, presents the United States with a dilemma. On the one hand, America has long argued for a more robust European contribution to defense, and the pre-Helsinki talk of Europe's creating a rapid-deployment capability is a step in the right direction. On the other hand, European-only defense schemes raise questions about Europe's commitment to its transatlantic ties. Sen. John McCain has worried out loud that Europe is drifting away from NATO, while others in the administration and Congress share the same concerns privately.

These misgivings are understandable, yet the right attitude for America is to welcome the Helsinki summit. The threat that a new European force might detract from NATO is less than the threat posed by European passivity. The Kosovo war exposed Europe's acute weakness: Despite having 2 million people in uniform, NATO's European members were hard put to get 40,000 troops to a war on their doorstep. This weakness threatens to corrode NATO. It breeds American resentment of European wimpishness and European resentment of American domination.

The Helsinki summit represents a start in addressing this problem. The Europeans say they want to be able to deploy 60,000 troops at short notice, and to sustain them in the battlefield for up to a year. This intention implies a welcome pledge to modernize forces that are currently designed to repel a Soviet ground attack. Europe needs to acquire the long-range transport equipment and other gear that would make its soldiers useful in post-Cold War missions.

But modernization is not all that is needed. To keep the transatlantic alliance healthy, Europe must do two further things. It must stick to its declared intention of integrating its new capability into NATO and of using it outside the alliance's umbrella only in situations where NATO's leadership has decided not to act. Second, Europe must reverse the decline in its defense budgets. America spends 3.2 percent of GDP on defense, but France spends 2.8 percent, Britain 2.6 percent and Germany a paltry 1.5 percent. It will be hard to convince Americans that Europe is serious about strengthening NATO until that gap narrows.