By DINA CAPPIELLOWASHINGTON (AP) â¿¿ The Obama administration will press ahead Friday with tough requirements for new coal-fired power plants, moving to impose for the first time strict limits on the pollution blamed for global warming. The proposal would help reshape where Americans get electricity, away from a coal-dependent past into a future fired by cleaner sources of energy. It's also a key step in President Barack Obama's global warming plans, because it would help end what he called "the limitless dumping of carbon pollution" from power plants. Although the proposed rule won't immediately affect plants already operating, it eventually would force the government to limit emissions from the existing power plant fleet, which accounts for a third of all U.S. greenhouse gas emissions. Obama has given the Environmental Protection Agency until next summer to propose those regulations. The EPA provided The Associated Press with details of the proposal prior to the official announcement, which was expected Friday morning. The public will have a chance to comment on the rule before it becomes final. Despite some tweaks, the rule packs the same punch as one announced last year, which was widely criticized by industry and Republicans as effectively banning any new coal projects in the U.S. That's because to meet the standard, new coal-fired power plants would need to install expensive technology to capture carbon dioxide and bury it underground. No coal-fired power plant has done that yet, in large part because of the cost. And those plants that the EPA points to as potential models, such as a coal plant being built in Kemper County, Miss., by Southern Co., have received hundreds of millions of dollars in federal grants and tax credits. Coal, which is already struggling to compete with cheap natural gas, accounts for 40 percent of U.S. electricity, a share that was already shrinking. And natural gas would need no additional pollution controls to comply.