China says it is facing serious power shortages as severe winter weather continues to cause unusually high demand for electricity.
China generates more than half its electricity from coal
Thirteen regions have already started to ration power supplies, the official Xinhua news agency reported.
It said coal reserves were down to emergency levels and stockpiles were only high enough to generate power for the whole country for eight days.
China's economic boom has led to surging demand for electricity.
The coal industry has struggled to keep up, partly because of the government's campaign to close many small mines on safety grounds.
China's National Development and Reform Commission, which has control over energy issues, has called on coal suppliers and electricity providers to do their best to maintain output while promoting energy conservation.
It said winter demand was at its peak, and that low water levels has caused hydroelectric output to fall, further driving demand for coal power.
The China Business News newspaper said that 70% of all coal deliveries were made by road, and that heavy snowfall and icy conditions had contributed to supply problems.