NATO leaders will seek ways to console Ukraine and Georgia at a summit on Thursday after failing to agree to open the door of the Western military alliance to the former Soviet republics.

The 26 leaders will also face concerns about stability in the Balkans after Greece blocked an invitation to Macedonia to join NATO due to a row over the former Yugoslav republic's name.

The double setback for U.S. President George W. Bush on the first day of his final NATO summit overshadowed agreement to invite two other Balkan countries -- Croatia and Albania -- to join the 26-nation defence alliance, and progress on extra troops for Afghanistan.

"It's not a question of defeat. I think the question will be if the alliance can come together and show that the door remains open," a senior U.S. official said after the leaders failed to reach consensus on admitting Ukraine and Georgia to NATO's Membership Action Plan - a gateway to eventual entry.

Germany and France had led opposition to the move, saying it was premature when public support for NATO was barely 30 percent in Ukraine and Georgia did not control all its territory due to frozen conflicts with Russian-backed separatists.

NATO spokesman James Appathurai played down any impression that Russia had succeeded in blocking the decision, saying the allies were united in rejecting any outside veto or influence.

However, Georgian President Mikhail Saakashvili warned earlier in the week that a rebuff for his country would amount to "appeasement" of Russia and embolden hardliners to make mischief in two breakaway Georgian regions.

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While France combined to deflect Bush's drive to extend the eastern borders of NATO right up to Russia's frontiers, it did deliver a boost for the alliance in its most challenging security mission in Afghanistan.

Appathurai said President Nicolas Sarkozy offered up to 1,000 extra French troops for the east of the country, enabling the United States to redeploy forces to the south, scene of the fiercest fighting with Taliban insurgents.

That in turn appeared to meet Canada's parliamentary conditions to keep troops in Afghanistan, where they have suffered heavy casualties at the hands of Islamist guerrillas.

"This is good news for Canada and good news for NATO," Sandra Buckler, spokeswoman for Prime Minister Stephen Harper, said in regard to the French and American troop commitments.

She would not, however, confirm that this definitively meets Canada's self-imposed requirements of 1,000 extra troops.

Appathurai said the leaders agreed both Ukraine and Georgia were entitled to apply to join NATO and that it was "not a matter of whether but of when". But he said he did not expect either to be granted a Membership Action Plan (MAP) this week.

That left the sensitive question of what consolation prize to give the two aspirants when their disappointed leaders join the NATO summiteers at lunch on Thursday.

Bush had strongly urged sceptical European allies earlier to reward both countries for their democratic revolutions and not to allow Moscow a veto over NATO decisions.

On the other enlargement issue, Spanish Foreign Minister Miguel Angel Moratinos told reporters: "For the moment, Greece is not in a position to agree to the entry of Macedonia, and it will be Croatia and Albania first."

Athens threatened to veto Skopje's entry over an unresolved dispute about the former Yugoslav republic's name, which is the same as the most northerly Greek province.

Analysts have said a rebuff for Macedonia could destabilise the ethnically divided state with knock-on regional effects.