Barack Obama has moved ahead with even tougher greenhouse gas cuts on American power plants, aiming to jolt the rest of the world into action.
In finalising the unprecedented pollution controls, The US president installed the core of his ambitious and controversial plan to drastically reduce overall American emissions, as he works to secure a legacy on fighting global warming.
Yet it will be up to Mr Obama's successor to implement his plan, which has faced steep Republican opposition from Capitol Hill to the 2016 campaign trail.
Opponents planned to sue immediately and to ask the courts to block the rule temporarily. Many states have threatened not to comply.
The Obama administration estimated the emissions limits will cost 8.4 billion dollars (£5.3bn) every year by 2030. The actual price will not be clear until states decide how they will reach their targets. But energy industry advocates said the revision makes Mr Obama's mandate even more burdensome, costly and difficult to achieve.
"They are wrong," Environmental Protection Agency administrator Gina McCarthy said flatly, accusing opponents of promulgating a "doomsday" scenario.
Last year, the Obama administration proposed the first greenhouse gas limits on existing power plants in US history, triggering a yearlong review and more than four million public comments.
Obama will now unveil the final rule publicly at an event at the White House.
"Climate change is not a problem for another generation," he said in a video posted to Facebook. "Not any more."
The final version imposes stricter carbon dioxide limits on states than was previously expected: a 32% cut by 2030, compared with 2005 levels, the White House said. Mr Obama's proposed version last year called only for a 30% cut.
Immediately, his plan began reverberating in the 2016 presidential race, with Hillary Clinton voicing her strong support and using it to criticise her Republican opponents for failing to offer a credible alternative.
But Republican presidential candidate Marco Rubio, a Florida senator, predicted electricity bills would go up for millions of Americans and called Mr Obama's policies on power plants "catastrophic".
Mr Obama's rule assigns customised targets to each state, then leaves it up to the state to determine how to meet them.
Prodded by Senate majority leader Mitch McConnell, a number of Republican governors have said they simply will not comply. If states refuse to submit plans the EPA has the authority to impose its own plan and McCarthy said the administration would release a model federal plan that states could adopt right away.