The Environmental Protection Agency on Tuesday gave the public 45 more days to weigh in on a plan that would for the first time curb the pollution blamed for global warming from the nation's coal-fired power plants. The agency said it was still aiming to finalize the rules by next summer. 

The agency has already received 750,000 comments on the plan it unveiled in early June, which proposes a 30 percent cut in carbon dioxide pollution by 2030 from 2005 levels. It is one of the most significant actions ever take by the U.S. government on global warming, and the EPA said it needed more time to get it right. 

The announcement comes a week after 53 U.S. senators asked for an additional two months, and a week before President Barack Obama is expected to speak at a United Nations climate summit aimed at making progress toward a new international agreement. 

The White House said in June 2013 that final rules to reduce carbon pollution from existing power plants would be issued no later than June 2015. 

The EPA said it was still working toward that deadline.