WASHINGTON -- Describing climate change as "one of the key challenges of our lifetime," President Barack Obama on Monday formally announced one of the most significant actions his administration has yet taken to address the issue.

"We're the first generation to feel the effects of climate change and the last generation that can do something about it," said Obama in an event in the White House's East Room, citing stronger storms, deeper droughts and longer wildfire seasons as evidence that the climate is changing. "This is our moment to get this right and leave something better for our kids."

Obama's remarks coincided with the release on Monday of a new set of regulations for U.S. power plants that call for a 32 percent reduction in greenhouse gas emissions, from 2005 levels, by 2030. The new regulations, which have taken about two years to draw up, are seen as the biggest step yet toward combating the emissions known to be altering the planet's atmosphere and contributing to global climate change.

The 1,560-page document containing rules for existing power plants sets individual state goals for reducing emissions, and will require each state to develop a plan for meeting those targets. States can take a variety of approaches, such as changing over to renewable energy sources, improving energy efficiency and shutting down heavily polluting coal-fired units. The EPA also issued final rules for new power plants that call for phasing out new coal-fired units unless there is technology in place that can capture and store carbon emissions.

Obama described the rules as the "single most important step that America has ever taken in the fight against climate change."

Obama said the rules would reduce carbon dioxide pollution by 870 million tons, the equivalent of what is produced by 108 million homes or 166 million cars. But he acknowledged that there is likely a battle ahead, as industry groups line up to fight the rules in court.

"There will be critics of what we're trying to do. There are cynics who will say it cannot be done," said Obama, reflecting on previous environmental challenges like acid rain and leaded gasoline. "We've heard the same stale arguments before," he continued, describing them as "scare-mongering tactics" and "excuses for inaction."

"We can figure this stuff out, as long as we're not lazy about it," Obama went on. "This is going to be hard. Dealing with climate change is going to be a challenge."