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 $8.4bn (£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 year-long review and more than four million public comments.
Obama will now unveil the final rule publicly at an event at the White House.