Biggest threat to alliance may be gap between armed forces of Europe and US.
It was to have been a showpiece of cooperation and self-reliance: a French-designed spy satellite that would give the European allies their own eye-in-the-sky, reducing their need to pay for American intelligence.
But Germany's fiscal woes now appear to have grounded the nascent Franco-German project, Helios II, and with it one of the few European efforts to narrow the United States' massive lead in military might.
The US lead - in everything from basics like logistics and transport to cutting-edge sensor and information warfare technologies - is growing ever wider. As it does, so are concerns that American forces could leap so far ahead of their 15 NATO partners that they could have difficulties communicating, planning, and even fighting together in the coming decades.
Left unresolved, the capability gap could produce an alliance that is hamstrung by fiscal and strategic differences and even more dependent on US forces.
"There is a risk over time of a three-tiered alliance, with the US able to do everything, a few allies doing a range of these things, and some allies who are not going to be technologically in the same league," warns Robert Hunter, the US ambassador to NATO. "This is going to be one of the most important issues in preventing the hollowing out of the alliance."
Such concerns are being aggravated by NATO's decision in July to open its doors to the former Communist Eastern European states of Hungary, Poland, and the Czech Republic. Even as talks on their admission gather speed, doubts persist over whether they can rebuild armies equipped with outdated Soviet technologies into assets that can contribute to NATO's strength.
A noticeable gap
"There is a very big gap between [Eastern European] militaries and the US military. But at the same time, there is a very big gap between their militaries and the European allies in NATO," says a French military officer.
Expansion will also impose new burdens on NATO's current European members. Armies structured for almost 50 years to defend their homelands against a Soviet invasion will have to acquire the abilities to deploy rapidly to the alliance's easternmost borders and beyond.