China's coal inventories at power plants remained normal despite recent record power generation, the National Development and Reform Commission said in a report on its website (www.ndrc.gov.cn).

But China has yet to face the most difficult period, Liu Tienan, one of the commission's deputy directors, was quoted as saying, although he noted that current thermal coal supply and demand was stable.

He did not give a reason for the expected challenges, although typically power demand increases in the summer months and coal shipments are subject to weather and other factors.

China's daily power generation surged to a new high of 13.179 billion kilowatt hours on July 7 and coal stocks in key power plants totaled 58.8 million tonnes as of July 8, enough for 18 days of generation, said the report.

Power supply and demand were roughly in balance nationwide but electricity supply in Guangdong was a bit tight, the report said.

Coal-burning power plants produce about 80 percent of national power output.