The economic troubles in Europe have been making it even more difficult for the governments of the continent to fund some often unpopular defense programs.

The situation threatens to hinder the NATO alliance's attempts to upgrade its ability to respond to unexpected crises anywhere in the world. The United States and its European allies could face setbacks if the alliance is degraded under the heavy weight of budget pressures currently facing its members.

When the U.N. Security Council held the vote in March to launch a mission to defend Libyan revolutionaries, NATO was the only military force that could accept the job.

The NATO alliance was able to dispatch aircraft and ships to protect and assist Libyan rebels and civilians, which ended up turning the tide of the uprising that ousted Moammar Gadhafi.

"Libya proved that there are no other choices. When the U.N. decides on a mission, who else but NATO could take it over?," said French Air Force General Stephane Abrial, NATO's supreme commander for transformation.

But that capability is being threatened by Europe's economic crisis, exacerbating the difficulty European leaders have had for years convincing their people that defense spending is important.

Former British defense official Daniel Korski, says Libya was a success for NATO's transformation efforts, but Europe's economic crisis and the budget-cutting effort in the United States could slow them down.

"We are living in an age of austerity, and people are cutting their defense budgets as much as they can, and in an uncoordinated fashion. So we are really seeing a very varied agenda being threatened evermore because different nations are basically cutting to survive, rather than to build capability," Korski said.

The former head of the European Union's defense agency, Nick Witney, says it is not so much a lack of money as a lack of coordination, and of interest in defense issues among ordinary Europeans.

"We are not actually short of defense spending in Europe. What we are short of is using it properly, spending it on the right things, spending it effectively together. And we do not do that because we do not take defense seriously," Witney said.

For General Abrial, that is a problem because he says it is impossible to predict where or when the next opportunity will arise or what military capability NATO will need to address it.

"We need to be ready, we need to have the necessary capabilities available to face any kind of operation across the spectrum, and we need to have these forces and these capabilities readily available when crisis emerges. We do not design the calendar," Abrial said.

General Abrial says NATO needs more resources, more coordination and more partners to meet its ambition to remain the world's premier defense alliance, and to develop new high-tech capabilities to defend against missile and cyber attacks.

One difficulty lies in the differing American and European views of NATO's purpose. American leaders tend to see NATO as a community of defense based on Western values. Ideally, NATO would have the capability to operate anywhere in the world to secure these values. In this way, the alliance allows the U.S. to intervene in foreign affairs as part of a coalition rather than a unilateral actor.

Europeans, however, who tend to embrace modern sort of pacifist value system, would prefer to view NATO as a collective defense apparatus, abandoning the more ambitious nation-building projects in favor of non-traditional security functions such as cyberdefense and Arctic security.