US President Barack Obama will Tuesday bypass climate change skeptics in Congress and order tough new rules to curb carbon emissions, citing a "moral obligation" to save a warming planet.
Obama will also commit to new international efforts to slow carbon pollution, including withdrawing US support for coal-fired power plants abroad and offering to discuss new initiatives with big emitters like India and China.
And he will pledge to prepare the United States for the impact of climate change, which his administration now no longer sees as a distant challenge, while seeking to boost renewable energy forms like wind and solar.
Obama will make the commitments in a speech at Georgetown University, laying out a national strategy that will mark his most serious bid yet to honor earlier promises to fight climate change.
But the specifics of much of his plan were unclear, and many of Obama's new rules could face court challenges that would delay their implementation.
The president will be using the executive powers of his office since Congress, where there is widespread skepticism of climate change science and fear about the economic impact of mitigation efforts, has refused to act.
As such, they will lack the sweep that legislative efforts would have in establishing a carbon emissions trading scheme and enforcing change in US energy policy.
Previewing the speech, aides said Obama will require the Environmental Protection Agency to work with states and industry to establish tough new carbon pollution standards for new and existing power plants.
Some opponents of his approach have warned that the plan could result in older coal-fired plants being taken offline and may thereby raise electricity prices for consumers, which could disproportionately hurt the poor.
Officials counter that the plan will reduce the amount of electricity used -- thereby reducing fuel bills.
The plan will make $8 billion in loan guarantees available to promote advanced fossil energy and efficiency projects to support investments in innovative technologies, officials familiar with the speech said.
It also directs the Department of the Interior to permit projects using renewable energy sources like wind and solar on public lands by 2020 to power more than six million homes.
Obama will also set a goal of reducing carbon pollution by three billion metric tons by 2030 -- a figure equivalent to more than half of the annual carbon pollution from the US energy sector.
US government scientists say that global temperatures last month tied with 1998 and 2005 as the third warmest for the month of May since record-keeping began in 1880.
Obama's speech will come a week after a World Bank report warned that severe hardships from global warming could be felt within a generation, and include widespread food shortages, unprecedented heat waves and intense cyclones.
Officials made clear that Obama would not use the speech to give a decision about the Keystone XL pipeline, a massive project to bring oil from Canada's tar sands to the US Gulf Coast that has been slammed by environmentalists.
They said a State Department study was still assessing a presidential permit transaction for the pipeline, which was not yet ready.
Some environmental campaigners expect Obama to approve the pipeline, but to argue that he has already taken rigorous efforts to fight climate change.
Climate and environmental groups praised Obama's speech in advance.
Larry Schweiger, president and CEO of the National Wildlife Federation, said his speech was an "important step in the journey to end industrial carbon pollution."
Bob Ward, policy and communications director at the Grantham Research Institute on Climate Change and the Environment at London School of Economics welcomed Obama's "personal leadership."
But he warned: "Without the support of Congress for new federal legislation, the president is fighting this battle with one hand tied behind his back."
And Bill Snape, of the Washington-based Center for Biological Diversity, said what Obama was proposing "isn't big enough, and doesn't move fast enough, to match the terrifying magnitude of the climate crisis."
Republicans however accused Obama of waging a "war on coal" that would slap onerous regulations and unreasonable environmental targets on power stations.
"Declaring a 'War on Coal' is tantamount to declaring a war on jobs," said the Senate's top Republican Mitch McConnell.
"It's tantamount to kicking the ladder out from beneath the feet of many Americans struggling in today's economy."