A federal court Friday put on hold a controversial Obama administration regulation aimed at reducing power plant pollution in 27 states that contributes to unhealthy air downwind.

More than a dozen electric power companies, municipal power plant operators and states had sought to delay the rules until the litigation plays out. A federal appeals court in Washington approved their request Friday.

The EPA, in a statement, said it was confident that the rule would ultimately be upheld on its merits. But the agency said it was "disappointing" the regulation's health benefits would be delayed, even if temporarily.

Republicans in Congress have attempted to block the rule using legislation, saying it would shutter some older, coal-fired power plants and kill jobs. While those efforts succeeded in the Republican-controlled House, the Senate — with the help of six Republicans — in November rejected an attempt to stay the regulation. And the White House had threatened to veto it.

The rule, finalized by the Environmental Protection Agency in July, replaces a 2005 Bush administration proposal that was rejected by a federal court.