The hottest bidding war in Olympic history looked set to go to the wire on Monday less than 48 hours before International Olympic Committee (IOC) members cast their votes for the five candidate cities.

Members, observers and delegations from London [Images], Madrid, Moscow [Images], New York and Paris were shaking their heads and declaring the vote "too close to call" as they gathered for the IOC session which will determine the host city for the 2012 Summer Games.

IOC president Jacques Rogge gave away no clues at a news conference on Monday.

"Whoever wins, it's going to be a prestigious city," he said. "I'm often asked who is going to be the winner. The winner will be the IOC."

Rogge has repeatedly said since arriving in Singapore for the IOC session that the vote looked too close to call, a view that has found growing support in the plush hotels housing the Olympic delegations.

Paris came to the city state of Singapore confident in their role as clear favourites but they seemed surprisingly nervous as their odds with British bookmakers slipped from 1-6 to 1-4.

London, Madrid and New York all seemed to be gathering greater momentum and only Moscow appeared to be without a realistic hope of winning.

London were at 11-4 with William Hill bookmakers (down from 7-2), Madrid 14-1 (from 20-1), New York 33-1 with Moscow trailing at 50-1.

The conversations and gossip in the corridors of the Olympic delegates' hotels suggested the race is almost certainly much closer than suggested by the odds.

There was a first, but brief, outbreak of tension between arch-rivals Paris and London when a British bid delegate told a news conference the Stade de France [Images] showpiece stadium in Paris is not ideal to stage athletics.

PARIS STADIUM

Jim Sloman, chief operating officer of the Sydney 2000 Games and a London team member, said: "The one thing you do have with the existing Paris stadium is that it's been built for football, it hasn't been built for athletics.

"Even though they had a world athletics championships there a couple of years ago, it still has sightline problems, while the London stadium will be built specifically for athletics."

The statement seemed to stray close to the edge of IOC guidelines that cities should refrain from criticising their rivals' facilities. But, after studying a transcript of the conference, Paris officials chose not to make a formal complaint.

Rogge stepped in to quell any potential row. "Nobody has stepped over the line," he said. "Had anyone gone over the line, I would have intervened."

Paris, conscious that as favourite their best tactic might be not to make any gaffes, kept a relatively low profile in Singapore and astonished the media by saying they would not be staging any news conferences on Tuesday, the last day before the vote.

London, meanwhile, featured Prime Minister Tony Blair [Images] who is in town for two days to meet and greet and shake as many hands as if he were involved in a British general election.

New York were parading mayor Michael Bloomberg, former first Lady, Senator Hillary Clinton [Images], and possibly the world's greatest sports personality, former heavyweight champion Muhammad Ali, before the media.

Paris were looking to President Jacques Chirac, who arrives in Singapore on Tuesday, to redress the balance and make a direct impact on IOC members in Paris's presentation to the session after Blair has returned to host the G8 Summit in Scotland.

Madrid officials were quietly confident that the closeness of the race would allow them to emerge a surprise winner and a defiant Moscow described themselves as "the historic choice".