IN A move likely to be a boost to the climate change talks in Copenhagen, America's Environmental Protection Agency has formally declared that greenhouse gases endanger human health.
The decision provides a potential alternative route for the US to curb greenhouse gases. It will give US President Barack Obama an avenue to regulate carbon dioxide emissions - with or without Congress.
The EPA could regulate sectors such as cars, trucks, power stations and other heavy industry by passing rules that do not require a congressional vote.
It also gives President Obama new moral authority to offer up cuts to US emissions despite Congress resistance, because the EPA could impose limits by regulation.
Two weeks ago the President said he wanted a 17 per cent cut on 2005 levels by 2020 as a mid-term goal for a cap-and-trade scheme that aims for an 83 per cent cut by 2050. The mid-term figure is highly controversial. It has passed the House of Representatives but faces difficulties in the Senate.
White House press secretary Robert Gibbs said on Monday that Mr Obama ''continues to strongly believe that the best way forward is through the passage of comprehensive energy legislation, the type of which previously passed the House and is being considered now on the Senate side''.
But he added that the Supreme Court ruling in 2007 that greenhouse gas emissions could be considered a pollutant and should be regulated by the EPA if it deemed they were hazardous to health, meant that ''some action'' had to be taken.
The thinly veiled threat of using the alternate path will focus the minds of the handful of Democrat Senators and most Republicans who have indicated that they will oppose the cap-and-trade legislation.
It also means that world leaders can be more confident that Mr Obama will implement any pledges to cut emissions made at Copenhagen. Mr Obama has now said he will attend at the end of the conference about December 18, when negotiations are expected to reach a conclusion.
Announcing that the EPA had made the finding that greenhouse gases pose a danger to human health and public welfare, administrator Lisa Jackson said: ''The threat is real. The EPA is now authorised and obligated to make reasonable efforts to reduce greenhouse gas emissions under the Clean Energy Act.''
The ruling has horrified US business groups. The conservative US Chamber of Commerce, which has been locked in a public war of words with the Obama Administration, said the EPA finding ''could result in a top-down command and control regime that will choke off growth by adding new mandates to virtually every major construction and renovation project''.
The National Association of Manufacturers said the EPA action would do little to combat climate change and ''is certain to come at a huge cost to the economy''.
Mr Obama is due to meet industry groups supportive of cap and trade this week to urge them to support his plan.
The US developments will also be studied closely by environmental groups in Australia. The NSW Land and Environment Court has ruled that CO2 is a pollutant that needs to be considered when major projects, such as power stations, are approved.
If the cap-and-trade emissions trading scheme fails to pass Australia's Senate next year, the state development approvals processes could provide a new avenue to regulate CO2.