President Obama pressed ahead Tuesday with his climate change agenda, calling for new regulations on coal-fired power plants and setting a new condition for the approval of the controversial Keystone pipeline.

"We need to act," Obama said, in an address at Georgetown University.

Even before he spoke, the president's proposal drew condemnation from the coal industry and lawmakers whose states rely on that industry for jobs.

Rep. Shelley Moore Capito, a Republican from West Virginia, said the proposal "could deliver an unrecoverable blow to coal-rich states" like hers.

But Obama claimed climate change is having "profound impacts" on the planet and must be addressed. He called for the U.S. to lead the world in a "coordinated assault" on the issue.

Going around Congress and unveiling what was likely to be his most controversial plank, Obama said he was ordering the Environmental Protection Agency to create the first-ever carbon emissions limits for existing power plants.

He said that while other toxic chemicals like mercury are regulated, power plants can dump "unlimited amounts" of carbon pollution.

"That's not right, it's not safe. And it needs to stop," Obama said.

Further, Obama weighed in for the first time in months on the contentious issue of the proposed Canada-to-Texas Keystone pipeline. As the State Department reviews the stalled project, Obama said it should only be approved if it doesn't significantly boost emissions.

"Our national interest will be served only if this project does not significantly exacerbate the problem of carbon pollution," he said. "The net effects of the pipeline's impact on our climate will be absolutely critical to determining whether this project is allowed to go forward."

Supporters who say the pipeline would have a minimal impact said the comment should signal "speedy approval." The State Department, though, is still proceeding with its evaluation. In the near-term, lawmakers appear to be most focused on his call for new power plant regulations.

An adviser's comment ahead of the speech caused additional turbulence for the administration, as critics seized on it to claim the administration was unfairly targeting the coal industry. Ahead of the speech, White House climate adviser Daniel P. Schrag reportedly told The New York Times that a "war on coal" is needed.

"The one thing the president really needs to do now is to begin the process of shutting down the conventional coal plants. Politically, the White House is hesitant to say they're having a war on coal. On the other hand, a war on coal is exactly what's needed," he said. Schrag is a geochemist and the head of Harvard University's Center for the Environment. He also sits on a White House advisory panel.

Republican lawmakers bristled at that remark. "It really encapsulates the attitude this administration holds in regard to states like mine," Republican Senate Leader Mitch McConnell, who represents coal-heavy Kentucky, said Tuesday.

The industry, as well, issued similar warnings on Tuesday.

Advocates of the industry argue that it has made strides toward making coal more environmentally friendly. According to the American Coalition for Clean Coal Electricity (ACCCE), 10 clean-coal technology plants have launched since 2011. Another five are under development or scheduled to come online.

Group President Robert M. "Mike" Duncan said EPA regulations have played a big role in the closure of nearly 290 coal plants so far this year.

"Further regulation could force even more plant closures," he said in a statement, claiming the industry is evolving to expand clean-coal technologies -- provided the federal government allows it to.

Obama took a confrontational tone during part of the speech. Toward the end, he said: "We don't have time for a meeting of the flat-earth society."

He listed a string of proposals. Among them, he said he is directing his administration to allow enough renewables on public lands to power 6 million homes by 2020, effectively doubling the capacity from solar, wind and geothermal projects on federal property.

Obama also called for $8 billion in federal loan guarantees to spur investment in technologies that can keep carbon dioxide produced by power plants from being released into the atmosphere.

In taking action on his own, Obama is also signaling he will no longer wait for lawmakers to act on climate change, and instead will seek ways to work around them.

The linchpin of Obama's plan, and the step activists say will have the most dramatic impact, involves the limits on carbon emissions for new and existing power plants. The Obama administration has already proposed controls on new plants, but those controls have been delayed and not yet finalized.

"This is the holy grail," said Melinda Pierce of Sierra Club, an environmental advocacy group. "That is the single biggest step he can take to help tackle carbon pollution."

Forty percent of U.S. carbon dioxide emissions, and one-third of greenhouse gases overall, come from electric power plants, according to the U.S. Energy Information Administration, the Energy Department's statistical agency.

It's unclear to what extent the plan can rein in the use of coal overall. While it may curb coal within the U.S., federal stats show the U.S. is shipping much of it overseas -- to be burned -- anyway.

Coal exports from the U.S. hit a record 13.6 million short tons in March, according to the Energy Information Administration.

Obama was laying out a broad vision Tuesday, without detailed emission targets or specifics about how they will be put in place. Instead, the president launched a process in which the Environmental Protection Agency will work with states to develop specific plans to rein in carbon emissions, with flexibility for each state's circumstances.

Obama raised climate change as a key second-term issue in his inaugural address in January, but has offered few details since. In his February State of the Union, he issued an ultimatum to lawmakers: "If Congress won't act soon to protect future generations, I will."

The poor prospects for getting any major climate legislation through a Republican-controlled House were on display last week when Speaker John Boehner responded to the prospect that Obama would put forth controls on existing power plants by deeming the idea "absolutely crazy."

"Why would you want to increase the cost of energy and kill more American jobs?" said Boehner, R-Ohio, echoing the warnings of some industry groups.

Sidestepping Congress by using executive action doesn't guarantee Obama smooth sailing. Lawmakers could introduce legislation to thwart Obama's efforts. And the rules for existing power plants will almost certainly face legal challenges in court. The Supreme Court has upheld the EPA's authority to regulate greenhouse gases under the Clean Air Act, but how the EPA goes about that effort remains largely uncharted waters.

Even if legal and political obstacles are overcome, it will take years for the new measures to be put in place, likely running up against the end of Obama's presidency or even beyond it. White House aides say that's one reason Obama is ensuring the process starts now, while there are still more than three years left in his final term.

Under the process outlined in the Clean Air Act, the EPA cannot act unilaterally, but must work with states to develop the standards, said Jonas Monast, an attorney who directs the climate and energy program at Duke University. An initial proposal will be followed by a months-long public comment period before the EPA can issue final guidance to states. Then the states must create actual plans for plants within their borders, a process likely to take the better part of a year.

Then the EPA has another four months to decide whether to approve each state's plan before the implementation period can start.

The Associated Press contributed to this report.