"The release of the National Plan on Climate Change has been postponed, it was supposed to be released... today," Xu Huaqing, director of the National Development and Reform Commission's energy research institute, told AFP.

Xu, who was a co-author of the report, said it aims to discuss how China should deal with climate-changing greenhouse gases over the next five years.

He refused to speculate on when the report would be published, or say why it had been postponed.

According to Yang Ailun, an expert on climate change at Greenpeace China, the delay was decided in a closed-door meeting at the reform commission, China's economic planning agency, last week.

"Greenpeace China regrets this postponement and urges the government to issue the report in a timely manner," she said.

One Chinese environment campaigner familiar with the process told AFP that the delay was due to fears by officials over the impact of measures to curb greenhouse gases on the nation's economic growth.

"It appears that lower-level officials are having difficulty putting information together that higher level officials are willing to approve," said the environmentalist, who did not want to be named.

"There is a lot of mathematics going on right now."

China, which relies on coal for around 70 percent of its energy needs, is set to overtake the United States as the world's largest emitter of greenhouse gases over the next two to three years.