China said it plans to cut acid-rain causing pollution from power stations by nearly two thirds over the next five years, promising intensified efforts to meet environmental goals that have so far been missed.

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China has said it will reduce emissions of major pollutants by 10 percent by 2010, but growth-driven local officials and industries have ignored the target and last year output of sulphur dioxide instead grew by 1.8 percent.

Officials have said the resulting acid rain affects a third of China's land mass, damaging crops and threatening food security.

The National Development and Reform Commission, which steers industrial policy, and the State Environmental Protection Administration issued rules late on Tuesday that target coal-burning power stations, as the government seeks to stick to the pollution reduction goal.

Beijing itself has pledged to clean up its polluted air in time for the Olympic Games in 2008, and the city's worst polluter the Shougang Iron and Steel Group is packing up and leaving.

Many power stations must install equipment to capture sulphur dioxide before it is released into the air, reducing emissions by 4.9 million tonnes a year, say the rules issued on the NDRC's Web site (www.sdpc.gov.cn).

Combined with shutting ageing plants, using cleaner coal and reducing energy consumption, the rules aim to reduce sulphur dioxide pollution by 61.4 percent to 5.02 tonnes in 2010, down from 13 million tonnes in 2005.

Many power plants now either do not have desulfurisation equipment or do not use the equipment they have because it is expensive to operate.

The new plan aims to prod power operators to become greener by offering tax rewards and punishing companies that let the equipment go idle. Plants that have pollution-reducing equipment will also be given favoured access to the electricity grid.