U.S. President George W. Bush set the stage for a clash at his final NATO summit on Wednesday by pressing reluctant west European allies to set former Soviet republics Georgia and Ukraine on a path to membership.
He also urged other allies to follow the example of France, Poland and host nation Romania in providing extra troops for NATO's battle against Islamist insurgents in Afghanistan.
"We expect our NATO allies to shoulder the burden necessary to succeed," Bush said after talks with Romanian President Traian Basescu before leaders of the 26-nation defence alliance were to open a three-day summit.
He said the West should reward democratic revolutions in Ukraine and Georgia by giving both countries the prospect of joining NATO, although Russia has opposed this.
"My country's position is clear -- NATO should welcome Georgia and Ukraine into the Membership Action Plan," he said, referring to a programme which is a gateway to membership.
France and Germany, backed by several smaller countries, have said Ukraine and Georgia do not meet NATO's criteria and the decision would be an unnecessary provocation to Moscow just before President-elect Dmitry Medvedev takes office.
German Chancellor Angela Merkel reaffirmed on arriving in Bucharest that both countries should have a long-term prospect of NATO membership, "but there is one difference with the United States: we believe the time for MAP is not ripe".
At stake is whether NATO pushes its European borders right up to the frontiers of Russia, with the exception of Belarus, or leaves a strategic buffer zone as the Kremlin wishes.
Secretary-General Jaap de Hoop Scheffer left the scope, timing and nature of planned expansion vague in a speech to youth leaders from alliance countries.
"I expect the summit will open NATO's doors to several new members from southeast Europe," he said, adding the alliance would also strengthen ties with other states in the Balkans and the Euro-Atlantic area, including Ukraine and Georgia.
Bush sought to soothe Russian anger over what Moscow sees as NATO's attempt to encroach on its sphere of influence, saying the Cold War was over and Russia was not the West's enemy.
Looking ahead to a weekend summit with Russian President Vladimir Putin, Bush said there could be an unprecedented level of strategic cooperation on missile defense and arms control.
To a journalist who said that farewell meeting was headed for a "diplomatic train wreck", the president said: "You call it a diplomatic train wreck ... and I call it an opportunity." The White House later said Bush would also meet Medvedev in Sochi.
Amid blanket security that shut down much of central Bucharest, police broke into a factory in Bucharest that has been rented by a group of anti-NATO protesters and took away 46 suspected activists for identity checks.
British Prime Minister Gordon Brown pleaded on arrival for fairer "burden sharing" among allies in Afghanistan, where British troops have suffered heavy casualties in fighting the Taliban in the south.
Many European allies have restricted their troops to quieter areas in the north and west.
Canadian Prime Minister Stephen Harper, whose soldiers have also had heavy losses in the southeast, said he was "very confident" NATO would receive sufficient pledges of extra forces for him to withdraw a threat to pull Canadian forces out.
‘Limit of the Manageable’
NATO summits are usually carefully choreographed to showcase pre-cooked agreements but the main enlargement decisions this time are to be agreed at an opening dinner, when Bush meets the French, German and other leaders.
Since decisions require unanimity, Washington will probably have to settle for a pledge of closer cooperation with Ukraine and Georgia and a commitment to review the issue at next year's 60th anniversary summit.
German Foreign Minister Frank-Walter Steinmeier was quoted by a German newspaper as saying NATO should not strain ties with Moscow beyond "the limit of the manageable".
A senior German diplomat, Wolfgang Ischinger, also rejected accusations by Georgian President Mikhail Saakashvili that Berlin's attitude was tantamount to appeasement of the Kremlin.
Another uncertain decision facing the leaders was over Macedonia's candidacy for NATO membership.
Greece has threatened to veto Skopje's entry over an unresolved dispute about the former Yugoslav republic's name.
Bush made clear Washington wanted Macedonia, along with Croatia and Albania, to be invited to join this week.
But Greek Foreign Minister Dora Bakoyanni said in Athens there was no time for a last-minute compromise.
"We have said that no solution means no invitation," she told reporters.
Merkel sounded gloomy on Macedonia's hopes, saying: "It's going to be very difficult.
We'll do everything up to the last minute to overcome this dispute." Diplomats said if Athens did not yield, leaders might try to issue a conditional invitation to Skopje, to be ratified once the name dispute was settled.