President Barack Obama vowed Monday to force US power plants to cut carbon emissions by 30 percent in his most ambitious action yet on climate change.

Acting on his own faced with steely opposition in Congress, Obama laid out a plan that would let the 50 states choose their own approaches as long as each enforces restrictions on carbon emissions. The cuts would average 30 percent nationwide by 2030 from 2005 levels.

The plan will help "make sure that future generations are able to enjoy this beautiful blue ball in the middle of space that we're part of," Obama said.

Power plants account for some 40 percent of US emissions of carbon dioxide, the most common greenhouse gas that contributes to the planet's warming temperatures. Signs have been mounting that the planet is experiencing serious climate change, with a UN panel of scientists warning in April that polluters needed to act urgently to avoid worst-case scenarios which could include increased droughts, storms and coastline destruction.

But amid political resistance on climate change, the Obama administration emphasized public health. Obama, speaking on a conference call of the American Lung Association, said the guidelines "will help protect the health of vulnerable Americans, including children and the elderly."

The Environmental Protection Agency, which is spearheading the rules, said that the emission cuts would prevent up to 6,600 premature deaths and up to 150,000 asthma attacks in children.

"This is not just about disappearing polar bears or melting ice caps. This is about protecting our health and our homes," the agency's administrator, Gina McCarthy, said as she declared a "moral obligation to act on climate."

- Republicans say Obama 'nuts' -

Obama's plan was swiftly denounced by lawmakers of the rival Republican Party, which is friendly with the energy industry.

"The president's plan is nuts. There's really no more succinct way to describe it," said House Speaker John Boehner. He urged Obama's Democratic Party, which controls the Senate, to "listen to the American people and stop this disaster."

Climate regulations have been fiercely resisted by the coal industry, which is concentrated in several states where it is a major employer. Coal, the dirtiest form of energy, accounted for 39 percent of US energy last year and would fall to 31 percent by 2030 under Obama's plan.

Senator Mitch McConnell, the Republican leader in the Senate who represents the coal state of Kentucky, said that Obama's plan amounted to a "unilateral dismantling of our own economic supremacy and the self-imposed destruction of one of our nation's main competitive advantages in the global economy."

"These new rules will cheer the far-left patrons of Washington liberals, but there is simply no question that our competitors around the world will eagerly replace whatever industry we lose as a result of these new rules," he said.

Obama said that he anticipated criticism that the plan would hurt the US economy, which contracted in the first quarter. Obama argued that the emission cuts would spur investment and increase energy efficiency, ultimately reducing electricity bills.

"What we've seen every time is that these claims are debunked when you actually give workers and businesses the tools and incentive they need to innovate," Obama said.

With states required to submit plans in June 2016 in the heat of an election season, Republican governors may try to throw legal challenges to the plan, although the Supreme Court has held up the Environmental Protection Agency's authority to regulate carbon dioxide.

An administration official said that the agency would draft its own plan if a state refused to comply.

- Boost for global efforts -

Obama's push comes as the clock ticks on a UN-backed goal of reaching a new global treaty on climate change at talks in Paris in late 2015. Negotiators meet in Bonn, Germany, from Wednesday to prepare for the talks.

A spokesman for UN Secretary General Ban Ki-moon hailed Obama's announcement as a "significant step" and called on all countries to "accelerate their efforts."

Connie Hedegaard, the European Union's climate action commissioner, said Obama's proposal was "the strongest action ever taken by the US government to fight climate change, which is good news and also shows that the United States is taking climate change seriously."

UN-backed conferences have set a goal of keeping global warming below two degrees Celsius (3.6 Fahrenheit) above pre-industrial levels -- a goal that scientists warn is increasingly elusive.