China has issued a larger-than-expected second batch of coal export quotas for this year of 15.9 million tons, trade sources said on Tuesday, as stocks pile up.

China issues export quotas in two batches each year. The second is normally granted in the middle of the year, but this has been delayed since the summer, as China grappled with severe power shortages caused by coal shortages ahead of the Olympics.

"It's irrelevant now," said an official at one of the Chinese coal exporters, "There is not enough time for us to sign contracts and export."

The quotas will be valid through the end of the year.

It brings the total coal export quotas for this year to 47.7 million tons.

China exported 35.7 million tons of coal in the first nine months of the year, down 6 percent from a year earlier, official customs data showed. The exports head mostly to Japan, South Korea and Taiwan.

Domestic coal demand growth has slowed since the end of the summer amid ample supply, and prices have been sliding.

Analysts said the government was likely feeling the heat from large stockpiles and thus handed out a bigger-than-expected second batch of quotas.

"The issuance is too late, and quotas are impossible to be fully utilized," said Wang Ye, an analyst at CITIC Securities Co.