**The US has declared greenhouse gases harmful to human health, paving the way to regulating emissions without the backing of Congress.**Lisa Jackson of the US Environmental Protection Agency (EPA) said the agency had finalised its so-called “endangerment finding”.
She said the EPA was now “authorised and obligated to make reasonable efforts” to cut greenhouse gases.
The EPA will now be able to act even if Congress fails to pass legislation.
The announcement cames as global climate talks got under way in Copenhagen.
The US House of Representatives passed a bill in June that would cap greenhouse gas emissions and establish a national carbon trading scheme.
But progress of a similar bill through the Senate is not likely before March at the earliest.
Public consultation
In April, the EPA decided that carbon dioxide and five other greenhouse gases may endanger human health and well-being.
The decision had to go into public consultation, giving people 60 days - until 23 June - to respond.
An EPA spokeswoman told the BBC that the agency had received more than 300,000 comments and had been working on its response since.
In 2007, the US Supreme Court instructed the agency to review the evidence on climate change with a view to reconsidering its stance on the possible threats of climate change.