BEIJING-- The leaders of some 50 countries have confirmed their attendance of the Beijing Olympic Games next year, Liu Qi, President of BOCOG (Beijing Organizing Committee for the Games of the XXIX Olympiad) said on Thursday.

At a briefing in New York, Liu reiterated Beijing's determination to fulfill its promise to improve the air quality and provide good conditions for the athletes from around the world.

Despite the progress made so far, Beijing still faces challenges, he said. The State Environmental Protection Administration (SEPA) and the Beijing municipality are working on measures to respond to any unexpected weather conditions and providing a good environment for the athletes in their competitions, he said.

"We will ensure a clean Olympics free of doping as we will use a sophisticated test center and enhance cooperation with the World Anti-Doping Agency," he said.

Liu said Beijing has enough volunteers to serve the Olympic and Paralympic Games next year as the number of the applicants has already surpassed what is required.