Nato's 60th anniversary summit next April will start with dinner in the spa of Baden-Baden, move to Strasbourg in France and then hop over the Rhine into Germany for final deliberations in the little town of Kehl.

This logistical nightmare for a two-day summit neatly sums up Nato's present confusion. It has become so multi-tasked, so desperate to get involved in everything from cyber warfare to anti-piracy and missile defence, let alone a hugely draining and complex campaign in Afghanistan, that it has lost its way. It has never settled into the new security era that followed the fall of the Iron Curtain and has ceased to be a cohesive and united alliance.

In the Cold War, Nato was a big player, hawking its views and expertise on the substantive issues of the day - arms control, nuclear non-proliferation, conventional force reductions, confidence-building measures. Today, it is a military alliance without any political clout.

In Afghanistan, for example, it has 50,000 troops throughout the country, but where is its political voice? Is Nato now just a troop-providing alliance that takes the flak when things go wrong and sacrifices its men and women without having a real say on the way forward for the country? This is one reason why the campaign there faces stalemate. Even in military terms, the alliance is not acting as a cohesive force in Afghanistan; individual member states present the US commander of its International Security Assistance Force (Isaf) with a kaleidoscope of national caveats that limit military action. There are even divisions between the US and Britain, the two biggest troop contributors, over strategy and tactics in the south, not a good omen for the arrival of 20,000 more US troops next year.

The United Nations and other international bodies are in the forefront of the political game in Afghanistan but Nato just sends troops. Its credibility is at stake but it lacks political firepower because it has no obvious role in designing a new regional framework that might bring greater stability not just to Afghanistan but to neighbouring countries, particularly Pakistan.

Where Nato has made a political stand, the consequences have been disastrous. Its enlargement programme, under which it has expanded in all directions, taking in the Balkans, the Baltic states and Eastern and Central Europe, has been promoted, particularly by the US, as a crusade for spreading democracy and security. In many ways, this has worked: the Balkans are more stable and the former Soviet satellites embraced reform and leapt with gratitude into the European family.

Times have changed, however. Russia is once again a force to be reckoned with, thanks to oil and gas reserves and Vladimir Putin's muscular foreign policy stance. Now Georgia and Ukraine stand at the open door, and it is too much for Nato to handle. The foreign ministers' meeting in Brussels on December 2 was a perfect example of the dilemma facing the 26 members. They were supposed to have seriously considered offering both former Soviet republics entry into the membership action plan (MAP), which would have led them to become embedded in Nato's training and reform programme.

The foreign ministers came up with a fudge that allowed Georgia and Ukraine to believe they were still loved without upsetting Moscow. The issue, however, has not gone away. The alliance is divided between those committed to the open-door policy - Washington being the most prominent - and newer arrivals, including Poland, the Czech Republic and the Baltic nations, who are worried about the way that Moscow is going, particularly after the mini-war in Georgia in August, and want Nato to focus more on its traditional role of territorial defence. Quite like old Cold War times.

How this division is resolved will depend to a large extent on Barack Obama. Will he follow the Bush line and keep that door open, even for Georgia and Ukraine, or will he reconsider priorities, focusing perhaps on ensuring that stability in the Balkans moves higher up the agenda? This would mean getting the Former Yugoslav Republic of Macedonia - there are still rows over its name - swiftly into the alliance and brokering an end to the interminable impasse between Greece and Turkey over Cyprus.

It's ironic that the President-elect has surrounded himself with Clinton Administration officials and appointed Hillary Clinton as Secretary of State. They will all be open-door enthusiasts, but it cannot make sense to focus on ensuring the future membership of Georgia and Ukraine, particularly while Mikhail Shakashvili, whose recklessness in trying to seize back the breakaway region of South Ossetia triggered the mini-war, is still President in Tbilisi.

Nato is in no position to offer an Article 5 guarantee - an attack on one member is an attack on all - to Georgia or Ukraine; yet there are ideological members of the alliance who believe that this fundamental principle must apply whatever the circumstances. If enlargement remains a priority under Mr Obama, this increasingly high-risk guarantee will need to be put into a more realistic context.

As Nato approaches its 60th anniversary, there will be no better time for it to come up with a new strategic concept that will transform it into a politically potent body capable of playing a part on the world stage. If not, the celebrations next year will merely cover up divisions that could lead the alliance to fall apart.

Michael Evans is defence editor of The Times

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