WASHINGTON — The Trump administration announced on Monday that it would take formal steps to repeal President Barack Obama’s signature policy to curb greenhouse gas emissions from power plants, setting up a bitter fight over the future of America’s efforts to tackle global warming.

At an event in eastern Kentucky, Scott Pruitt, the head of the Environmental Protection Agency, said that his predecessors had departed from regulatory norms in crafting the Clean Power Plan, which was finalized in 2015 and would have pushed states to move away from coal in favor of sources of electricity that produce fewer carbon emissions.

“The war on coal is over,” Mr. Pruitt said. “Tomorrow in Washington, D.C., I will be signing a proposed rule to roll back the Clean Power Plan. No better place to make that announcement than Hazard, Ky.”

The repeal proposal, which will be filed in the Federal Register on Tuesday, fulfills a promise President Trump made to eradicate his predecessor’s environmental legacy. Eliminating the Clean Power Plan makes it less likely that the United States can fulfill its promise as part of the Paris climate agreement to ratchet down emissions that are warming the planet and contributing to heat waves and sea-level rise. Mr. Trump has vowed to abandon that international accord.