BEIJING — Beijing's city government said today it ordered half its cars off the road leading up to the Olympics in an effort to clean up the air for the games and save energy.

Half of all government and Communist Party cars will not be used starting July 19, the city said in a notice on its Web site.

From July 20, another regulation kicks in that will allow vehicles on the road only on odd or even days, depending on their license plate number.

"To meet the air quality standards and to realize safe and smooth traffic is our solemn promise to the international community," the Beijing government notice said.

New sports venues and $40 billion spent to improve China's infrastructure have not disguised the fact that Beijing's air quality remains a contentious issue for the games.

International Olympic Committee president Jacques Rogge had said outdoor endurance events lasting more than an hour will be postponed if air quality is poor.

Organizers announced details last week of a plan to pull half of Beijing's 3.3 million vehicles off the roads during the Olympics to help clean the city's noxious air for the games.

The auto ban is part of an anti-pollution plan that also will halt construction and heavy industry during the Olympics, which begin in seven weeks.

Under one plan, vehicles will be allowed on the roads on alternate days — according to even or odd car registration numbers — from July 20 until Sept. 20.

In addition, 300,000 heavy polluting vehicles — aging industrial trucks, many of which operate only at night — will be banned from July 1.