WASHINGTON (AFP) - With one eye on his legacy, United States President Barack Obama will Monday unveil what he called the "biggest, most important step we've ever taken" in the fight against climate change.
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 pollution from the nation's power plants, setting limits on power-plant carbon emissions for the first time.
Plants will have to reduce carbon dioxide emissions by 32 per cent from 2005 levels by 2030, in an ambitious drive which will boost the renewable-energy sector but which is already facing stern opposition.
Obama will deliver his eagerly anticipated remarks at the White House at 2.15pm (2.15am).
Laying out how climate change is a threat to the economy, health and security of America, and adding that time was of the essence, Obama said in a video released early Sunday: "Climate change is not a problem for another generation. Not any more.
"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.
- Hot-button issue -
In the coming months, Obama is expected to visit Alaska to highlight the impact of climate change and will host Pope Francis at the White House, when they are expected to make an impassioned and collective call for action.
With the end of his presidency drawing nearer, Obama argued in the video that the plans will lead to lower energy bills in the future for Americans, create jobs in the renewable energy sector and ensure more reliable energy services.
Quite simply, he said, the US 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.
In its initial proposal a year ago, the Obama administration had set the carbon emissions cut from the power sector at 30 per cent.
The tough 32 per cent collective reduction drew fierce opposition from the Republican Party, which described the measures as "overreach" and "heavy-handed", and said they would have "devastating consequences for our economy."
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.
- 'War on coal'? -
In the video, Obama said that global warming and the reasons behind it were backed up by scientific data - some Republican opponents dispute the existence of global warming and others cast doubt on whether humans are to blame for the phenomenon.
But it is not only Republicans who have voiced alarm: opponents in the energy industry have also hit out at Obama's initiative, accusing him of waging a "war on coal".
Gina McCarthy, head of the Environmental Protection Agency, insisted the rules were "reasonable" and "achievable".
"They can cut carbon pollution in whatever way makes the most sense to them," McCarthy said.
"No plant has to meet them alone or all at once, they have to meet them as part of the grid and over time."
Hillary Clinton, the Democrat hoping to take over from Obama after the 2016 election, welcomed the announcement as a "significant step forward in meeting the urgent threat of climate change.
"And it drives investments in clean energy and energy efficiency, reduces asthma attacks and premature deaths, and promotes a healthier environment and a stronger economy."