"Because Bush's Environmental Protection Agency continues to wantonly ignore its duty to regulate pollution, California is forced to seek judicial action."

Brown also said that under federal law the EPA was authorised to regulate greenhouse gases on ocean-going vessels and aircraft, as well as agricultural, construction and industrial equipment.

'Failing to act'

Brown accused the EPA of failing to act to combat pollution from those sources and said California would sue if it failed to enforce regulations within six months.

The lawsuit threat comes one week after Californian environmental regulators approved stringent guidelines aimed at forcing ocean-going vessels visiting the state's ports to use cleaner fuel.

Arnold Schwarzenegger, the governor of California, has made the environment a key issue of his tenure, signing a bill in 2006 that saw the state become the first in the US to impose limits on global warming gases.

Earlier this year California and 17 other states sued the EPA for failing to limit greenhouse gas emissions from new cars and trucks despite a ruling by the US Supreme Court a year earlier that the agency had the power to do so.

The EPA had blocked the states from regulating greenhouse gas emissions from new cars and trucks, with Stephen Johnson, the EPA administrator, saying California's proposed emissions limits were not needed because the US congress had passed energy legislation raising fuel-economy standards that achieve similar results.

However, California officials say the national fuel standards are not as stringent and appealed the decision in state and federal courts.

The EPA has also been heavily criticised by Democrats in congress, with three senators calling for Johnson's resignation, saying he had failed to fight global warming and other ecological problems.

Brown said that Connecticut and Oregon states, New York City, the California Air Resources Board, the South Coast Air Quality Management District and an a coalition of environmental groups would also join the proposed suit, Reuters reported.