Rescheduling “would not be necessary for all sports,” Mr Rogge said. “But definitely the endurance sports like the cycling race, where you have to compete for six hours; these are examples of competitions that might be postponed or delayed to another day.”

“We are going to put the athletes' health first. We'll have contingency plans in action,” he added. Some events might even be moved to other venues.

Pollution figures are alarming. Beijing has seen 140 days with clear skies this year, including yesterday; that is four days less than the same period last year. The concentration of air pollutants is always high and frequently over maximum levels, but the authorities sound reassuring and pledge the problem will be tackled.

Beijing organisers promise to take 1.3 million of the city's 3 million cars off the roads from Aug. 8 to 24 next year. A trial run is expected next week, British Olympic Association chief executive Simon Clegg said.

Li Zhanjun, from the BOCOG, confirmed the trial plan but refused to go into further details before a press

According to Gilbert van Kerckhove, an adviser to the Olympic organisers, the city plans to shut all the factories in and around Beijing at least three months ahead of the Games and almost all infrastructure construction would be banned next year to reduce dust and other pollutants.

Yesterday a raft of celebrations marked the one-year countdown to the opening of the Games under a clear sky, a great break from the preceding smog-filled days.

Last night’s centrepiece celebration was in Tiananmen Square. Thousands of officials and invited guests were entertained by a phalanx of singers and dancers.

An array of national leaders, led by National People's Congress chairman Wu Bangguo, took to the podium between the performances to address the crowd, reiterating Beijing's determination to stage the best-ever Olympics.

“It has been a century-long dream for the Chinese to host an Olympic Games,” Wu said. “With these Games, the Chinese will have better understanding and cooperation with the rest of the world.”

China’s leaders might be moved to make speeches about the country’s rising star and national pride, but in many parts of the world activists, lawmakers and Chinese dissidents chose instead to remember human rights violations in China and Tibet, the lack of political and media freedom, and China’s support for states like Sudan.

Many also remembered the millions of low-paid migrant workers exploited to build the great Olympic facilities and venues as well as the seizure of tens of thousands of homes in Beijing and the closure of thousands of schools for migrants.