As the 28 leaders of the North Atlantic Treaty Organization gather in Strasbourg and Kehl, the world's most important multilateral alliance is in crisis. 60 years on from its founding in the aftermath of World War Two, NATO has evolved into a two-tier alliance split between those who fight and those who do not. On one side of the NATO divide is a small group of Anglosphere nations - Britain, America and Canada - plus stalwarts like the Poles and the Dutch, who possess a martial warrior ethos; on the other is a sizeable number of European countries who treat the alliance as little more than a glorified peacekeeping force.

NATO is also under threat from Franco-German plans to develop a European Union defence identity with its own army and headquarters, as well as growing Russian intimidation that is at present succeeding in blocking the organization's eastward expansion. NATO is being further undermined by a failure on the part of most of its members to maintain defence spending at required levels.

For both President Obama and Prime Minister Brown, the top priority at this week's summit must be to secure greater European involvement in the war in Afghanistan, the biggest test for the NATO alliance since the end of the Cold War. Barack Obama recently announced the deployment of an additional 4,000 troops to join the 17,000 who are being mobilized as part of a planned U.S.-led surge against the Taliban, under the overall leadership of General David Petraeus. British defence chiefs are considering the deployment of a further 2,000 soldiers to boost British troop numbers in Helmand Province.

So far, there is no evidence that major European allies are showing any enthusiasm for sending more troops. For years, opponents of the Iraq War in continental Europe claimed it was a distraction from the fight against the Taliban and al-Qaeda, and that the United States had its priorities wrong. Now the war in Iraq is drawing to a close, and America is dramatically expanding its forces on the Afghan front, there has been a distinct lack of enthusiasm across Europe to match the U.S. commitment.

The current breakdown of contributions to the NATO-led International Security Assistance Force (ISAF) is heavily lopsided. Over two thirds of the 62,000 soldiers serving in ISAF are from English-speaking nations, including 30,000 from the U.S., 8,300 from the UK and nearly 3,000 from Canada. Australia, a NATO partner, has over a thousand troops in the field. Great Britain alone has almost as many personnel in Afghanistan as continental Europe's big four combined - France, Germany, Italy and Spain, who have just 9,500 troops deployed between them. Once the additional 21,000 American troops are on the ground, the 'Anglosphere' contingent will make up more than three quarters of total ISAF numbers.

The casualty figures in Afghanistan demonstrate the overwhelming sacrifice made by the English-speaking countries. Out of the 1,123 NATO troops killed in the Afghanistan war, 951 (85 percent) are from the U.S., UK, Canada and Australia. Britain alone has sacrificed 152 servicemen and women in Afghanistan, almost the same number, 168, lost by all the other European contingents combined. 116 Canadian soldiers have been killed, almost five percent of their total deployment. In contrast to most of their European compatriots (the Dutch and Poles excluded), British and Canadian forces are deployed in the battlefields of southern Afghanistan. The majority of European forces are placed well away from the main war zones, and in many cases are shielded by dozens of "caveats" negotiated by their governments, aimed at keeping them out of harm's way.

The stakes of the Afghan operation are extremely high. The consequences of failure for NATO forces are unthinkable. Afghanistan must never again be allowed to become a safe haven for the Taliban and its al-Qaeda cohorts, with a return to the medieval-style savagery of the pre-9/11 era. It would be used once again as a launch pad for major terrorist attacks, with western Europe particularly vulnerable. A failure to defeat the Taliban would be also be a huge humiliation for the NATO alliance from which it would likely never recover, dramatically reducing its ambitions and resulting even in its eventual dissolution.

If it is to survive for another six decades, NATO needs a new commitment from all of its members. It is time for French President Nicolas Sarkozy, German Chancellor Angela Merkel and other European leaders to step up to the plate and commit their troops and resources to the defeat of the West's enemies in Afghanistan. If Afghanistan does fall again to the Taliban and the followers of Osama Bin Laden, the terrorists who will flourish within its borders will make no distinction between bombing New York, London, Paris or Berlin.

It is unacceptable that British and American soldiers are laying down their lives for the security of the free world, while much of Europe watches from the sidelines with callous indifference. President Obama has made winning the war in Afghanistan Washington's top foreign policy priority - he must do all in his power to persuade European partners it should be theirs too.

Nile Gardiner is Director of the Margaret Thatcher Centre for Freedom at the Heritage Foundation in Washington, DC.