Obama to unveil 'biggest step ever' in climate fight

US President Barack Obama will tomorrow unveil what he called the "biggest, most important step we've ever taken" to fight climate change, a sensitive issue central to his legacy.

The White House will release the final version of America's Clean Power Plan, a set of environmental rules and regulations that will home in on the pollution from the nation's existing power plants, setting limits on power-plant carbon emissions for the first time.

Laying out how climate change is a threat to the economy, health, wellbeing and security of America, and adding that time was of the essence, Obama said in a video released early today: "Climate change is not a problem for another generation. Not anymore."

"Power plants are the single biggest source of harmful carbon pollution that contributes to climate change," added Obama, who made the battle against climate change a core promise of his 2008 election campaign.

"But until now there have been no federal limits to the amount of that pollution that those plants can dump into the air."

He added that without imposing the unprecedented limits, "existing power plants can still dump unlimited amounts of harmful carbon pollution into the air weekly.

"For the sake of our kids, for the health and safety of all Americans, that's about to change."

Power plants account for some 40 per cent of US emissions of carbon dioxide, the most common greenhouse gas that contributes to climate change.

With the end of his presidency drawing ever nearer, Obama argued that the plans will lead to lower energy bills in the future for everyday Americans, create jobs in the renewable energy sector and ensure more reliable energy services.

Quite simply, he said, the United States and the rest of the world need to act now to save the planet, ahead of a major meeting of world powers in Paris in December tasked with doing just that.

The new plan sets a goal of cutting carbon pollution from power plants by 32 per cent by 2030 compared with 2005 levels, The Washington Post said.

In his initial proposal a year ago, the target was 30 per cent.

But the move is likely to face fierce opposition from numerous sides, including political rivals and industry groups, as well as possible legal challenges.

Climate change is a hot-button issue in American politics, and cuts are politically sensitive because coal, among the dirtiest energy sources, remains a major US industry.

Even as natural gas gains in popularity, hundreds of coal-fired power plants dotted across the country provide about 37 per cent of the US electricity supply, ahead of natural gas and nuclear energy.