Washington: Calling it a moral obligation, President Barack Obama unveiled the final version of his plan to dramatically cut emissions from U.S. power plants, as he warned anew that climate change will threaten future generations if left unchecked.

Touting the plan at a White House event on Monday, Obama said the unprecedented carbon dioxide limits are the "the single most important step" America has ever taken to fight climate change.

He warned that because the problem is so large, if the world doesn't get it right quickly, it may become impossible to reverse, leaving populations unable to adapt.