The US Environmental Protection Agency has cleared the way for regulation of greenhouse gases, without laws being passed by Congress.
The move reflects President Barack Obama's commitment to act on climate change as he prepares to travel to the climate change summit in Copenhagen.
The EPA ruling that greenhouse gases endanger human health, widely expected after it issued a preliminary finding earlier this year, will allow the agency to regulate planet-warming gases even without legislation in Congress, reports Reuters.
The agency could begin to make rules as soon as next year to regulate emissions from power utilities and heavy industry under existing laws.
Clearing the way for regulation is expected to inject some optimism into the two-week United Nations meeting in Copenhagen, but has been criticized by some US business groups who fear it could push up costs.
The US Supreme Court ruled in 2007 that the EPA had the right to regulate emissions of the gases under the Clean Air Act. But under the administration of former President George W. Bush, the EPA said Congress was the right place to frame action.