The two countries' environmental protection agencies signed an agreement kicking off a pilot program to identify how many of Beijing's vehicles can be retrofitted with cleaner engines and particulate filters, officials said.

The program will also see the US Environmental Protection Agency (EPA) and China's State Environmental Protection Administration (SEPA) work together to reduce sulfur levels in fuel used in China.

If the program is successful, it could potentially generate significant benefits for the United States, the world's biggest car maker.

Officials said the US could eventually export its emission control technology to China, the third largest and one of the fastest growing vehicle markets in the world.

Beijing, which is hosting the 2008 Olympic Games, hopes to significantly clean up air quality by 2008.

By next year, it plans to reduce the sulfur level in diesel fuel it uses to 350 parts per million -- at which point the vehicles would be able to US control technology that can reduce emissions by 30 to 40 percent.

Environmentalists have urged China not to emulate the US' car-focused culture and put more emphasis on building public transpont but Chinese officials Wednesday said they had no choice but to deal with car emissions which now are one of the top two pollution sources in Beijing, along with coal.

"We encourage the development of public transportation and the control of the number of cars but at the same time we need to reduce pollution from cars," said Li Xinmin, SEPA's deputy director general.

The program will begin by checking 15 to 20 buses in Beijing to see if the technology can be applied to them. The US agency is hoping to replicate the project throughout China.

"Given the fast growth of China's economy and transportation sector, vehicle emissions will be the biggest problem in China in coming years," said Margo Oge, the EPA's director of transportation and air quality.

While the United States is the world's biggest emitter of greenhouse gas, much of it caused by vehicle emissions, China, the second biggest, is fast catching up due to rapid modernization. It is projected to exceed US emissions by around 2020.

"The US has been working to reduce vehicle emissions and wants to share its technology with China. It is also concerned China's pollution will make its away across the Pacific Ocean to the United States," said Ren Hongyan, project officer for the SEPA.

All rights reserved. � 2005 Agence France-Presse. Sections of the information displayed on this page (dispatches, photographs, logos) are protected by intellectual property rights owned by Agence France-Presse. As a consequence, you may not copy, reproduce, modify, transmit, publish, display or in any way commercially exploit any of the content of this section without the prior written consent of Agence France-Presse.