President Obama’s plan to curb climate change could transform American energy, potentially dealing a blow to the coal-fired power plants that supply much of the nation’s electricity but also pump planet-warming gases into the atmosphere.

Obama rolled out his long-awaited plan in a speech Tuesday that outlined broad goals but left the specifics to be worked out over the coming months.

“The question now is whether we will have the courage to act before it is too late,” he said in a speech at Georgetown University. “And how we answer will have a profound impact on the world we leave behind, not just to you but to your children and your grandchildren.”

The president signaled for the first time that he will block the controversial Keystone pipeline if it’s shown that it would worsen climate change. Keystone would tap Canadian oil sands that produce more greenhouse gases than other sources, but the State Department downplayed the climate impact in a highly disputed report. “The pipeline’s impact on our climate will be absolutely critical in determining whether this project will go forward,” Obama said.

The overall plan the president rolled out calls for boosting renewable energy and efficiency standards for appliances and federal buildings, and preparing the nation for the extreme weather impacts of a changing planet.

The centerpiece of Obama’s blueprint is his promise to limit the greenhouse gas emissions of America’s power plants. The plants produce an estimated 40 percent of the nation’s carbon dioxide emissions that scientists link to global warming.

His proposed new regulations could increase utility costs for American consumers and harm regional economies tied to coal, which generates about 37 percent of all U.S. electricity.

Coal state senators called the proposed regulations a “war on coal” that would hurt the economies and jobs in their states and the entire country.

“Declaring a ‘war on coal’ is tantamount to declaring a ‘war on jobs.’ It’s tantamount to kicking the ladder out from beneath the feet of many Americans struggling in today’s economy,” said Sen. Mitch McConnell, R-Ky., the Senate minority leader.

“Removing coal from our energy mix will have disastrous consequences for our recovering economy,” said Sen. Joe Manchin, D-W.Va. “These policies punish American businesses by putting them at a competitive disadvantage with our global competitors. And those competitors burn seven-eighths of the world’s coal, and they’re not going to stop using coal anytime soon.”

Kevin Book, an analyst at Washington-based ClearView Energy Partners, said it was reasonable to assume that Obama’s climate change policies would lead to marginally higher bills for utility customers.

“Cleaner is almost always more expensive,” Book said. “But clean is not usually as expensive as initially feared.”

New carbon pollution limits, combined with previously announced mercury rules, could mean a major wave of coal-fired power plant closures over the next decade, Book said. The Obama administration already has been working on carbon pollution rules for new coal-fired plants that could mean that few, if any, of those are built, Book said.

Jeff Holmstead, who represents utility clients at the Washington law firm Bracewell and Giuliani, said it wasn’t clear how far the Environmental Protection Agency could go legally in limiting greenhouse gases.

It’s too soon to tell what impact Obama’s plan may have, he said. “There was no substance at all to the president’s proposal, he just said, ‘EPA, go develop a regulation on a certain timetable,’ ” Holmstead said.

The Natural Resources Defense Council estimates that it would cost at least $4 billion for utilities to comply with new regulations. The environmental group estimates as much as $25 billion to $60 billion in benefits, however, including the health benefits of switching to energy sources that produce less soot.

Obama said criticism of his plan as a job-killer showed a lack of faith in American business and ingenuity. A low-carbon energy economy can drive growth, he said, and the nation must tackle climate change.

“We don’t have time for a meeting of the flat earth society,” he said. “Sticking your head in the sand might make you feel safer but it’s not going to protect you from the coming storm.”

The president left the details to be settled later. He’s directing the EPA to work with states and industry to set the new pollution standards. He wants the rules finalized by June 2015.