The Trump administration has rolled back a landmark Obama-era effort targeting coal-fired power plants and their climate-damaging pollution.It's replacing the Obama rule with a less ambitious one that gives states more discretion in regulating those power plants.U.S. Environmental Protection Agency chief Andrew Wheeler said it's a sign that "fossil fuels will continue to be an important part of the mix" in the U.S. energy supply.U.S. President Donald Trump campaigned partly on a pledge to bring back the U.S. coal industry, which has been hit hard by competition from cheaper natural gas and renewable energy.The rule will go into effect shortly after publication in the Federal Register. Environmental groups pledge court challenges.The Clean Power Plan was one of former U.S. President Barack Obama's signature efforts to curb climate-changing emissions.EPA administrator Andrew Wheeler speaks with the media at the Environmental Protection Agency, Wednesday in Washington. Wheeler signed a repeal of the Clean Power Plan, adopting an alternative plan that would loosen regulations on the plants. (Alex Brandon/The Associated Press)Critics of the Obama administration say it overstepped its legal authority in issuing the power plant rule. Those opposing the rollback say it will worsen climate change and increase deaths from coal-plant pollution.Wheeler said he expects an increase in coal plants as a result of the repeal. Wheeler spoke to reporters after signing the final version of the repeal.The Obama-era plan sought to fight climate change by prodding coal-fired power plants out of the nation's electrical grid.Wheeler says the administration's repeal will lead investors to put money into more coal plants.U.S. coal-plant closings have reached near record numbers in recent years owing to competition from cheaper natural gas and renewable energy.'A stunning giveaway to big polluters'New York's attorney general said the state will sue to block the rollback.Attorney General Letitia James announced the state's intentions on Twitter shortly after the EPA replaced the rule, making a reference to the administration's "DirtyPower rule."She tweeted that it's "another prime example of this administration's attempt to rollback critical regulations that will have devastating impacts on both the safety & health of our nation.By repealing the historic Obama-Era Clean Power Plan & replacing it with a Dirty Power Scam, @realDonaldTrump’s Admin gives special interests the greenlight to worsen the climate crisis & put our children & communities' health at risk. https://t.co/Fi961zfFsV—@SpeakerPelosiHouse Speaker Nancy Pelosi, a Democrat, said the rollback is "a stunning giveaway to big polluters."Pelosi said in a statement that climate change is "the existential threat of our time" and that the administration is ignoring scientific studies about climate change and yielding to special interests.