BEIJING — As fireworks exploded over Tiananmen Square on Wednesday night, a troupe of 200 youthful singers on a glittering stage below belted out the theme song to mark the one-year countdown for the Beijing Olympics: "We Are Ready."

Make that almost ready.

The city's filthy air, which International Olympic Committee President Jacques Rogge warned could force the rescheduling of some events, is an embarrassment for the most expensive and anticipated Olympics in a generation.

Rogge's comments earlier in the day took nothing away from the 2 ½-hour show, broadcast live across China. Actor Jackie Chan and basketball player Yao Ming had their brief moments onstage, sharing it with ethnic dancers, flashy costumes and China's top officials, who promised the games will showcase the country's rising political and economic clout.

"On this very day next year, the Beijing Olympics will be declared open," said Liu Qi, president of the Beijing organizing committee. "People from all over the world are looking forward to that day."

Rogge was a perfect guest among 10,000 people attending the show, saying China was "opening itself to the world in new ways" and that the Olympic venues "look fantastic."

Hours before, however, the normally cautious Belgian was blunt, warning that the thick smog that has blanketed Beijing for months might force some events to be postponed.

"Yes, this is an option," Rogge told CNN. "It would not be necessary for all sports, sports with short durations would not be a problem. 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."

Few locals heard his comments, which were aired on foreign TV unavailable to the average Chinese.

By coincidence, Wednesday's skies were clearer, but it was muggy with temperatures in the low 90s — typical for August. The air is sure to be even cleaner a year from now, as factories will be closed, construction will be slowed and 1 million of Beijing's 3.3 million cars will be banned from the roads by China's authoritarian government.

"We want to take this opportunity to show the world that the people of China are committed to the success of the games and we believe we will deliver it," said Wu Bangguo, head of China's parliament and the Communist Party's No. 2 ranking official.

The ceremony's timing — the eighth day of the eighth month at 8 p.m. — was specially chosen: Eight is considered an auspicious number in Chinese because it rhymes with the word for "prosper."