BRUSSELS -- Alarmed by years of cuts to military spending, the NATO secretary general, Anders Fogh Rasmussen, issued a dire public warning to European nations, noting that together they had slashed $45 billion, or the equivalent of Germany's entire military budget, endangering the alliance's viability, its mission and its relationship with the United States.
That was two years ago. Since then, with the Afghan war winding down and pressure from the European Union to limit budget deficits, Europe has only cut deeper.
Now, as President Obama wrestles with his own huge budget deficit and military costs, the responsibility for keeping NATO afloat has fallen disproportionately onto the United States, an especially untenable situation as priorities shift to Asia.
The United States finances nearly three quarters of all military spending among NATO's 28 nations, up from 63 percent in 2001. And yet, across Europe, experts note, only the United States, Britain and Greece are meeting NATO's own spending guidelines of 2 percent of gross domestic product. Even Britain and France - the two leading European nations willing to project military might – are slipping further. France says that by 2014 it may cut deeper still -- to just 1.3 percent of G.D.P. down from 1.9 percent this year. By comparison, the United States spent 4.8 percent of its G.D.P. in 2011.
In 2012, for the first time, military spending among Asian nations, in particular China, exceeded that of the Europeans.
"We are moving toward a Europe that is a combination of the unable and the unwilling,'' said Camille Grand, a French military expert who directs the Foundation for Strategic Research. "European countries are continuing to be free riders, instead of working seriously to see how to act together."
Increasingly, without United States assistance, military experts said, Europe's armed forces have trouble carrying out basic operations as its dwindling financial and political commitment has derailed multiple initiatives intended to make the continent more self-reliant.
NATO's deputy secretary-general, Alexander R. Vershbow, a former senior Defense Department official, said that "the financial crisis has been corrosive to the alliance'' and that relations between the European Union and NATO remain "dysfunctional.''
Even as Britain and France have boasted of operations in Libya and Mali, those interventions have revealed Europe's weakness more than its strength. In Libya, the United States supplied intelligence, drones, fighter and refueling aircraft, ammunition stocks and missiles to destroy air defenses, and in Mali the French required American intelligence, drones, refueling and transport aircraft.
Senior American officials have warned that unless European countries spend more on defense, they risk "collective military irrelevance.'' A senior American official said that the Washington is eager for partnership in the Middle East and Asia, but "Europe's decision to abdicate on defense spending increasingly means it can't take care of itself, and it can't be a valuable partner to us.''
While the United States would like to be able to rely more on its European allies, many experts doubt that even the strongest among them, Britain and France, could carry out their part of another Libya operation now, and certainly not in a few years. Both are struggling to maintain their own nuclear deterrents as well as mobile, modern armed forces. The situation in Britain is so bad that American officials are quietly urging London to drop its expensive nuclear deterrent. "Either they can be a nuclear power and nothing else or a real military partner,'' a senior American official said.
The challenge is particularly acute as NATO pulls its forces out of Afghanistan after a long, wearying and unsatisfying war, with results widely seen as fragile, even unsustainable. After Afghanistan, with Europeans looking inward and the Russian threat considered more rhetorical than real, some wonder once more about the real utility of NATO.
James M. Goldgeier, dean of the School of International Service at American University in Washington, thinks that NATO has some considerable soul-searching ahead if its European members become increasingly unwilling to operate abroad. "If NATO isn't outward looking, it's got nothing to do,'' he said. "It can't go back to managing a threat from Russia, because it's not a real threat.''
A decade of halting European efforts to create a Common Security and Defense Policy has yielded little. A NATO Response Force, agreed to in 2002, was supposed to be an all-terrain rapid reaction force, with rotating membership for land, air, naval and special forces, ready to go anywhere and do most anything with at least 13,000 troops. But it has never been used, except in part to add security to the 2004 Athens Olympic Games and the 2004 Afghan elections and to provide disaster relief.
The European Union had a 1999 goal of 60,000 troops available for battle in a "Eurocorps." That has been quietly abandoned, replaced by battle groups of from 1,500 to 2,500 troops, also on a rotating basis among the many and differently equipped member states. The "lead'' country is supposed to take the political risk, provide most of the troops and most of the money.
"Not every battle group has been what it's made out to be,'' said Tomas Valasek, a defense expert and president of the Central European Policy Institute in Bratislava, with diplomatic understatement. "Some are more ready than others.''
But the will to participate has also declined. While the intent was to have two battle groups, a shortage of countries willing to participate has meant a quiet halving of ready forces to one battle group.
There is also a French-German brigade, formed in 1987, of some 5,000 men, which proudly marched down the Champs-Élysées on Bastille Day. But it, too, has remained unused. When the French wanted to use it for Mali, the Germans objected. "It's given military cooperation a bad name,'' Mr. Valasek said. The brigade was supposed to be the foundation for the Eurocorps, the abandoned goal of 60,000 troops ready to deploy for two months, but the reality has been embarrassing.
The Germans also objected to fighting in Libya, and even the European Union's effort to come up with 550 military trainers to help reconstruct the Malian army became a slow slog of negotiations and preparations; the first of those trainers has only now arrived.
There have been many discussions of how smaller European countries can share capabilities, the way the Balts do, and the Dutch and Belgians do for naval training and ship purchasing. There is an old debate about whether some countries will give up their own capabilities – air forces or navies, for example -- so long as partners agree to protect them. "The way forward is to permanently pool training, procurement, logistics and maintenance,'' Mr. Valasek said. "We won't find any more money any time soon.'' In the meantime, lack of procurement means a steady decline as older weapons systems become obsolete.
Toomas Hendrik Ilves, the president of NATO member Estonia, said that "it's time for a serious rethink about security policy.'' The United States "has made it clear that it won't continue to pay what is now 75 percent of all NATO military spending,'' he said. "That should be sufficient for the European members of NATO to understand that this can't work as now,'' especially with the rise of China.
A West European ambassador to NATO said that "we need to think more about how to share the burden and rebalance it, both in decision-making and responsibility,'' especially with the pivot to Asia. France, he said, sees the pivot "as an opportunity, while the East Europeans see it as a threat.'' After Afghanistan, he said, "we need an adult conversation about rebalancing.''
James B. Steinberg, a former deputy secretary of state and deputy national security adviser, now dean of the Maxwell School at Syracuse University, said that Washington could cope. "There's less strategic focus on the remaining security problems in Europe itself,'' which he described as mostly residual, including the Balkans and a post-Soviet equilibrium. That means Washington will not put more resources into Europe, especially as it concentrates on China.
But on broader strategic challenges, including China, Washington "likes the partnership with Europe for political legitimacy, which is not a function of its military capacity,'' he said. European political support allows the United States to take a broader position in East Asia that is not simply bilateral.
No one knows where the next crisis will emerge, Mr. Steinberg said, but it is useful to have NATO there, even acting as a limited coalition, as in Libya. If the United States represents 75 percent of NATO spending, "that's a modest price to pay when the next crisis comes along.''
Whatever NATO's weaknesses, "if it were gone, it would be very, very hard to recreate."
This article originally appeared in The New York Times.