WASHINGTON • A divided United States Supreme Court has blocked a new federal regulation that would cut emissions from power plants, putting a hold on President Barack Obama's most ambitious effort to combat climate change.

The justices, in a 5-4 order, heeded calls from utilities, coal miners and more than two dozen states to halt the Environmental Protection Agency (EPA) rule while court challenges go forward.

Foes say the agency is overstepping its authority and intruding on states' rights. Supreme Court intervention casts doubt on the legal prospects for the programme, suggesting concerns among a majority of the nine justices.

The court action on Tuesday "confirms that the legal justification for the Clean Power Plan should be examined by the courts" before state and private resources are used to develop state plans, said Ms Melissa McHenry, a spokesman for American Electric Power, one of the biggest coal users among US utilities.

The delay is a blow to Mr Obama's environmental agenda, highlighting the prospect that his signature programme for combating climate change could be in legal jeopardy. It also risks undermining the US commitment to pare greenhouse gas emissions as part of an international accord reached in Paris last December. The delay is a setback for the EPA, which had been largely on a winning streak before the federal judiciary.

The EPA rule, known as the Clean Power Plan, requires states and utilities to use less coal and more wind power, solar power or natural gas. The programme is designed to bring about cuts of 32 per cent in carbon emissions from power plants by 2030.

The delay will last at least until a federal appeals court in Washington rules on the plan, probably later this year after it hears arguments in June. If the utilities and states lose in that court, the delay would continue while they sought Supreme Court review.

The environment agency will not be able to enforce a Sept 6 deadline for states to either submit their emission reduction plans or request a two-year extension.

Mr David Doniger, director of the climate and clean air programme at the Natural Resources Defence Council, which supports the plan, said that states, financial leaders and other interests will continue pushing to clean up the power sector and "will keep moving to incorporate strategies and public policies leading towards a clean energy economy".

But Mr Jeff Holmstead, a former EPA assistant administrator, said the delay is sure to chill action by states to comply with the plan.

"The states that have frantically been trying to figure out how to comply certainly put their pens down tonight," he said.

The Supreme Court gave the EPA victories in 2013 and 2014, upholding its greenhouse-gas permitting rules and regulation of pollution that crosses state lines. It also rejected a plea to reconsider its 2007 decision letting the agency regulate greenhouse gases.

But last year, the court sent EPA's far-reaching rule on mercury emissions back to the agency for further analysis, a decision that has had no practical impact so far but was raised as a reason the court should grant this delay.

"The stay is a signal the Supreme Court has serious concerns with the power plan," said Mr Mike Duncan, president of the American Coalition for Clean Coal Electricity, which includes coal-burning utilities, producers and rail operators.

"We are optimistic the power plan will ultimately be rejected."

BLOOMBERG