President Bush has thrown down the gauntlet to Russia and set the stage for a showdown with Europe by expressing public support for Ukraine and Georgia to become members of Nato,
Mr Bush said after talks with Ukraine's President, Viktor Yushchenko, that America "strongly supports" the former Soviet republic's bid for membership. "In Bucharest this week, I will continue to make America's position clear: we support Map for Ukraine and Georgia." Map refers to Nato's membership action plan for future members.
Nato itself is divided over whether to offer the two former Soviet republics a path towards Nato membership. France and Germany want to avoid antagonising Russia, which is opposed to Ukrainian and Georgian membership, and the26-member military alliance operates on the basis of political consensus.
Mr Bush said the outcome of the Nato meeting should not be prejudged, but the French Prime Minister said yesterday: "France will not give its green light to the entry of Ukraine and Georgia. We think that it is not the correct response to the balance of power in Europe, and between Europe and Russia."
Other states, however, are concerned about Russia – which is not a Nato member – having what amounts to a veto over Nato membership. Mr Bush said he had been assured by other Nato leaders "Russia will not have a veto over what happens in Bucharest. I take their word for it."
President Vladimir Putin, attending his last major international summit before he becomes prime minister next month, will hold talks in Bucharest with Nato leaders. Nine former members of the Soviet bloc are already Nato members.
Mr Putin's spokesman, Dmitry Peskov, warned Ukraine and Georgia that membership would "lead to additional tension". In a telephone briefing from the Kremlin with foreign reporters, he did not respond directly when asked about possible linkage between the membership issue and a dispute with America over plans to locate parts of a US missile defence shield in Poland and the Czech Republic.
Mr Bush, who is expected to discuss the missile shield with Mr Putin at their final summit in the Russian resort of Sochi next weekend, has rejected any trade-off.
Mr Peskov said Russia would prefer the US to shelve its deployment plans, but added: "We appreciate the effort from our American partners, and we are ready to continue our mutual search for the way out of this very complicated situation" which he said affected Russia's strategic and national security interests.
The Nato summit is expected to extend invitations to at least two countries – Albania and Croatia – to join the alliance. A third invitation had been expected for Macedonia. However, Greece repeated yesterday that it would veto Macedonia joining unless there was an agreement with Athens on the country's name.
There has been a dispute for 15 years over Macedonia which has the same name as a northern Greek province over which it is accused of having territorial claims. It has UN membership under the provisional name of the Former Yugoslav Republic of Macedonia.