IOC admits Internet censorship deal with China

The city has already banned cars from roads on alternate days under an odd-and-even license plate scheme, suspended some factory production and opened new subway lines to try to clear its notorious pollution.

"The likelihood of needing stronger measures is very small," said Zhu Tong, a professor at Peking University and leader of a technical group advising Games organizers on air quality.

Slightly cooler temperatures and rain on Tuesday have thinned the haze, but with below-par air quality readings on several days since the emergency measures took effect on July 20, worries remain about athletes wheezing air laced with fumes and dust.

Experts said that given the size of Beijing, the volume of pollutants that flow into the city from other parts of China, and the short time period before the Games open on August 8, there was little more that could be done.

"In this short a time-frame, even if you took all the personal cars off the highway, you might see another 10 percent improvement, but it would be small," said Staci Simonich, an analytical chemist at Oregon State University who has been studying Beijing's air quality.

"The best thing that could happen during the Games is to have it rain every night," she said.

China also has other issues on its mind, including security in the restive region of Tibet, where official media said Chinese police had been mobilized to ensure "absolute security without a single lapse".

The remote region erupted into rioting in March that sparked protests across China's ethnic Tibetan areas and brought into focus international criticism of Beijing's policies on the issue.

The Tibet Daily announced on Wednesday tough policing during the Games on top of a sweeping security crackdown already in place. China is at pains to avoid any shows of defiance by pro-Tibet independence groups that could embarrass the government before a worldwide audience.

(Additional reporting by Emma Graham-Harrison, Lindsay Beck, Chris Buckley, Liu Zhen and Simon Rabinovitch; Writing by Lindsay Beck; Editing by Sanjeev Miglani)

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