Beijing is striving for fresher air and bluer skies for its residents.

Facing worsened air quality, city authorities called on Monday for new tactics in the war against air pollution.

Shi Hanmin, director of the Beijing Environmental Protection Bureau, said the number of good days was only a little more than 100 during the first half of the year.

That is five days less than the same period last year, which recorded the best air quality in the capital in recent years.

Worse, there were seven days with heavy air pollution in the past six months. Not a single day of heavy contamination was reported in 2003.

Shi attributed the deterioration partially to Beijing's special weather conditions this year. Among other things, the frequent fog and static weather kept minor pollutants from diffusing.

Shi's department wants to put a brake on pollution and create 230 days free from air contamination. However, nature and existing policies have made it very difficult to achieve this year's pollution-fighting goals, said Shi.

Current conditions, however, make it impossible to substantially improve air quality in the second half of this year.

To bring about a blue sky for some 14 million Beijingers, the bureau has been urged to intensify its efforts against pollution.

On top of the city's construction sites and road surfaces - large sources of floating dust - as well as roofs of buildings in some key areas will be required to go through regular cleanings to cut down on floating particles.

Monitoring facilities will be set up at construction sites that create serious pollutions, to try and reduce it.

Other departments such as construction, traffic, city administration and quality inspection have also been encouraged to participate in the effort to cut down pollution.

The Beijing Municipal Committee of Communications may ban buses more than 10 years old as well as diesel-engine busses that fail to meet the European I emission standard.

In addition, the committee will upgrade around 10,000 taxis.

At the same time, construction sites that cause floating dust pollution may risk being forced to cease operation.

The city's quality inspection authority vowed to eliminate low-quality fuel oil from the capital.

Vice-Mayor Ji Lin said the city's goal is to have a "Green Olympics" in 2008.

During the 2008 Olympic Games, the city's air quality is expected to meet the national standard every day.