A federal appeals court on Thursday turned down a request from 27 states to put on hold new regulations that are the central pillar of President Barack Obama's efforts to control global warming pollution.

The states, led by West Virginia and supported by coal and other fossil fuel industries, had asked the court to stay the rules, known as the Clean Power Plan, pending a decision on the merits of their challenge. The rules are intended to sharply reduce emissions of carbon dioxide from existing electric power plants over the next 15 years.

The litigation will continue, probably eventually reaching the Supreme Court, whose landmark 2007 ruling opened the door to controlling greenhouse gas emissions under the Clean Air Act. The Clean Power Plan, along with rules increasing the energy efficiency of automobiles, is one of the strongest federal policies ever to limit carbon dioxide emissions.

Now the lawsuit seeking to overturn Obama's rules will play out along with the initial implementation of the regulations. They require states to file compliance plans starting later this year or face the imposition of a federal plan.

"Winning isn't everything, but in this case it's pretty close," said Carol M. Browner, a former climate advisor to Obama who led the Environmental Protection Agency during the Clinton administration.

The U.S. Court of Appeals for the District of Columbia Circuit set an expedited briefing schedule for the litigation, reflecting the significance of the most far-reaching of federal economic regulations. That is "indicative of the seriousness with which the court is taking the case and the very substantial legal issues that need to be resolved," said Scott Segal of the Electric Reliability Coordinating Council, which had been critical of the rules.

Briefs are due in mid-April, with oral arguments scheduled for early June. The court's ruling could come by the fall, but a Supreme Court appeal could spill into 2017.

The partisan split over the regulations, which most Republicans in Congress and the party's leading presidential candidates oppose, makes any legislative rejection of the Obama policy unlikely at least until after the 2016 election.

This was the second time the appeals court had refused to preemptively block the rules. That signalled that it would rather consider the appeal on a normal track, but not how it was leaning on the legality of the policy.

By now, each side's arguments are familiar, and the court urged them to keep their briefs concise.

Opponents claim that the EPA exceeded its authority in several ways. The central issue, however, is whether the agency may regulate this type of pollution from power plants not just at the smokestack, but through measures that involve energy efficiency, fuel switching, and even the trading of carbon credits.

Proponents say that the approach chosen by the agency has ample precedent, gives maximum flexibility to the states, and is the most cost-effective.

Had the appeals court agreed to put the rules on hold, that would have presented the legal equivalent of a short-circuit to the whole electric utility system, from the power companies and their fuel suppliers to the complex interstate regulatory apparatus.

And the shock would have been felt around the world. Without controlling emissions from coal-fired power plants, the United States cannot possibly live up to its pledges under the new global climate treaty signed in Paris last month.

For a stay, the challengers would have had to convince the appeals court they would suffer immediate and lasting harm, and that the merits of the case leaned strongly in their favor.

The refusal of the three-judge panel to do so, announced in a brief order, was thus a significant victory for the Obama administration and its environmentalist allies.

"The decision greenlights work that most states have already begun to put the Clean Power Plan into action, and signals to others that there is no excuse for holding back on implementation," said David Doniger of the Natural Resources Defense Council.

Kevin Kennedy of the World Resources Institute said it would give states "the chance to seize the ample economic opportunities available in a low carbon economy."

But Thomas Pyle of the American Energy Alliance, a group that favors fossil fuels over clean-energy alternatives, urged recalcitrant states to "remain steadfast in their opposition to this unlawful regulation."

However vocal and determined, the opposition is far from monolithic.

Almost as many states favor the rules as sued to block them, and their legal case supporting the EPA is at least as strong. Among them are California and the populous Northeastern states, which already have carbon emissions trading schemes in place. They say they can readily meet the pollution reduction goals.

Many local governments, regulatory agencies, and utility companies – along with providers of solar and wind power – also have asked the court to uphold the regulations.

In one of many declarations filed with the court by those who support the EPA's regulations, Edith Chang, the deputy executive officer of the California Air Resources Board, said that any delay would "impair greenhouse gas reduction efforts at the state, national, and international levels, create uncertainties in California's functioning emissions market, potentially delay compliance deadlines resulting in extended periods of elevated greenhouse gas emissions exacerbating climate risk to California, and impose unnecessary additional planning and process coordination costs on California and similarly situated states."