NATO, the North Atlantic Treaty Organisation, is a remarkable case of institutional survival in the face of changing circumstances. It was created in 1949 to protect Western Europe from the Soviet threat, which vanished in 1989. Yet NATO not only survived the collapse of the Soviet Union but expanded, taking in former satellite states of Eastern Europe and even the Baltic republics that had been part of the Russian Empire for more than two centuries. But the Georgian debacle could break NATO.

In those Eastern European countries that were so recently ruled from Moscow, the presence of Russian troops in Georgia has reawakened old fears. On Thursday, Poland hastily agreed to let the United States place anti-ballistic missile sites on its soil, on condition that there must also be a full-fledged US military base in the country. Why? Because then, if Russia attacked Poland, the US would become involved.

The rhetoric in the new NATO members has been almost as hysterical as that in Georgia, where President Mikhail Saakashvili has been calling the Russians "21st century barbarians" who "despise everything new, everything modern, everything European, everything civilised". Similar rhetoric pervades the universe of the US media, where the fact that it was Georgia that started this war by unleashing an artillery barrage on South Ossetia and then invading it has been virtually erased from the story-line.

It?s a rousing morality tale that hits the right notes for an American sensibility, and it?s not just Georgia?s PR firms that are pushing this line. It?s also the US State Department and the Pentagon, which had been building Georgia up as a key US ally on Russia?s southern flank. Yet US Secretary of State Condoleezza Rice looked uncomfortable on Friday in Tbilisi as she stood beside Saakashvili.

Perhaps she was pondering the fact that while the "new Europe" of former Soviet-bloc countries uncritically backs Georgia and the US commitment there, the "old Europe" of Germany, France, Italy and their neighbours mostly does not. This is a problem if she wishes to bring Georgia and Ukraine into NATO, since "old Europe" is the core of NATO, with three times the population and five times the wealth of "new Europe".

Angela Merkel, the German chancellor, put it carefully after meeting Russian President on Friday: "Some of Russia?s actions were disproportionate (but) it is rare that all the blame is on one side. In fact, both sides are probably to blame. That is very important to understand."

The Italian government warned against trying to build an "anti-Moscow coalition". French Foreign Minister Bernard Kouchner works for the most pro-American French President in recent history, Nicolas Sarkozy, but he still said:"Don?t ask us who?s good and who?s bad here.

We shouldn?t make any moral judgments on this war."

This will be seen as "appeasement" by the neo-conservatives who still rule the roost in Washington, but many in Western Europe would call it common sense. The Russians will stay in Georgia until they have dismantled the Georgian army and navy bases that could threaten the enclaves of South Ossetia and Abkhasia again, removing all the new American weaponry that gave Georgia an offensive military capability, and then they will withdraw to the enclaves as the ceasefire agreement requires.

Sarkozy brokered that ceasefire, and agreed to write those clauses into it. He knew that they allowed Russian forces to stay on Georgian territory until the military threat had been nullified, and accepted them. He did so as he did not really see Russia as an aggressor (although he will not contradict America publicly by saying it). But if the US pursues its goal of bringing Georgia and Ukraine into NATO, there are only three options.

If "old Europe" refuses, on the grounds that it does not need Russia as an enemy, then either the US drops its demand, or NATO breaks up. The third alternative (and perhaps the likeliest) is that "old Europe" lets the two former Soviet republics join - but with the unspoken reservation that they will never actually go to war with Russia to protect them.

That would be a less dramatic end for NATO, but it would be an end. A two-tier alliance is no alliance at all.