But with the opening of the Games just 160 days away, mainland analysts said the move was more symbolic than substantial.

The adoption of the National IV emissions standard - the equivalent of Euro IV - was consistent with the capital's pollution control efforts in the lead-up to the Games, said Beijing environmental protection bureau spokesman Du Shaozhong .

'With the implementation of more stringent environmental standards and tougher pollution control measures, [we will] cut emissions of pollutants as much as possible and ensure good air quality during the event,' he said at a briefing set up by Olympics organisers this week.

Huang Xiyue , an automotive expert at Chongqing University, said the policy would not make much difference to the capital's air quality in the short term.

'It is good news for Beijingers in the long run as it becomes the first city to implement the more exacting and environmentally friendly emissions standard,' Professor Huang said.

The policy was in the public interest and would help the country's battle against widespread pollution, he said, but the authorities should be cautious about promoting the stricter standard in other cities because they were likely to upset many people, including car buyers and manufacturers, who would suffer from higher vehicle costs.

'It would be too costly to eliminate a large number of cars from the market simply because of emissions standards,' he said. 'Domestic carmakers will have some difficulties coping with the imposition of the new policy on short notice.'

Many car buyers in the capital said they would not mind paying an extra 1,000 yuan (HK$1,096) or 2,000 yuan to buy a greener car.

'I think I will attach high importance to the emissions standard when I choose a car,' said Wang Yue, an office clerk who visited the Beijing Asian Games Village Automobile Exchange, the biggest market for new and second-hand cars in the capital yesterday.

But the significance of the move, unveiled about two weeks ago, has been questioned by analysts and car dealers.

Beijing has said it will not lift a ban on diesel-fuelled light vehicles despite concerns over their higher emissions of pollutants, especially particulate matter.

Mr Du cited the difficulty in controlling emissions from diesel cars and Beijing's much-criticised choking air quality and frequent winter smog to explain the ban.

But experts said the ban had exposed the discord between the environmental watchdog and planning authorities, who hoped to promote domestic car brands and encourage the use of diesel engines.

Wang Canfa , an environmental expert at the China University of Political Science and Law, also noted that the new standard would not apply to the more than 3 million cars already on the road in Beijing.

'I don't know how much difference the policy will make to the city's air quality,' Professor Wang said. 'It is especially so as we know pollution statistics are not accurate at all in the first place.'

Yao Zhichao , a sales manager at Beijing Asian Games Village Automobile Exchange, said yesterday that cars complying with the older Euro III standard still dominated the market.

He doubted the ban on the sale of Euro III-compliant cars in Beijing could be implemented immediately.

'All the cars here, Euro IV-compliant or not, have gone through emissions tests under the existing standards, and I don't see the possibility for vehicle manufacturers to recall the cars that are not up to the Euro IV standard,' he said.

Guo He , a First Automobile Works vehicle dealer at the exchange, said many domestic carmakers were not ready for the stricter emissions standards.

'Apart from Brilliance China, Jinbei Automobile and a few others that began to promote Euro IV-compliant cars by the end of last year, we have not seen new cars meeting the new standard from many other domestic carmakers,' he said.

Mr Guo said carmakers had lowered prices about a week ago to attract buyers and promote sales after the Lunar New Year holiday.

Sales of Volkswagen's Jetta, one of the most popular passenger cars, showed a modest rise in the past three weeks, with its price dropping from 73,800 yuan to 70,300 yuan.

Shanghai will not follow Beijing's move any time soon, according to the Shanghai Evening Post.

Applying the brakes

This year, the new standards are expected to bring about these reductions in emissions:

Carbon monoxide: 48,000 tonnes

Hydrocarbons: 5,300 tonnes

Nitrogen oxides: 4,100 tonnes