Heather Zichal, White House coordinator for energy and climate change, said Obama would announce climate policy initiatives in the coming weeks.
Another official told The New York Times Obama could outline the new policy as early as next week.
Obama called on Congress in his Feb. 12 State of the Union address to take action on climate change.
"But if Congress won't act soon to protect future generations, I will," he said. "I will direct my Cabinet to come up with executive actions we can take, now and in the future, to reduce pollution, prepare our communities for the consequences of climate change, and speed the transition to more sustainable sources of energy."
Experts cited by the Times say if Obama hopes to have new greenhouse gas standards for utilities in place while he's still in office, he needs to start this year.
"He is serious about making it a second-term priority," Zichal told the Washington forum Wednesday. "He knows this is a legacy issue."
The policy will use the Environmental Protection Agency's authority under the Clean Air Act to regulate heat-trapping pollution from coal-fired power plants, Zichal said.
"The EPA has been working very hard on rules that focus specifically on greenhouse gases from the coal sector," Zichal said. "They're doing a lot of important work in that space."
She did not specifically mention new standards for existing power plants, but other administration officials told the Times Obama was working on such regulations.
The plans were first reported by the Los Angeles Times Tuesday.
A 2007 Supreme Court decision affirmed the EPA's mandate to regulate greenhouse gases, and the agency has already done so by mandating, for instance, new gasoline formulations sold in many states from May to September.
The EPA last year proposed greenhouse gas regulations for new power plants but has not imposed carbon standards on existing plants.
Fossil-fuel plants are the largest U.S. source of global-warming pollution, The New York Times said, responsible for nearly 40 percent of greenhouse gas emissions.
Obama's policy address is also expected to include new initiatives for renewable power and energy efficiency, including making appliances and industrial equipment more efficient and reducing energy wasted in public and private buildings, Zichal said.
The policy to limit greenhouse gases from fossil-fuel power plants -- which convert heat energy from combustion into mechanical energy that operates electrical generators -- will likely provoke legal challenges from Republicans and several industries, both newspapers said.
Republican lawmakers largely reject the idea human activity causes climate change.
GOP leaders, including House Energy and Commerce Subcommittee on Energy and Power Chairman Edward Whitfield, R-Ky., had no immediate comment.
The Edison Electric Institute, the power industry's trade group, declined to comment.
In Berlin Wednesday, Obama spoke about the issue in an address to about 4,500 people in front of the Brandenburg Gate.
"The effort to slow climate change requires bold action," he said. "And on this, Germany and Europe have led.
"In the United States, we have recently doubled our renewable energy from clean sources like wind and solar power. We're doubling fuel efficiency on our cars. Our dangerous carbon emissions have come down. But we know we have to do more -- and we will do more," he said to applause.
"For the grim alternative affects all nations -- more severe storms, more famine and floods, new waves of refugees, coastlines that vanish, oceans that rise," he said. "This is the future we must avert. This is the global threat of our time.
"And for the sake of future generations, our generation must move toward a global compact to confront a changing climate before it is too late," Obama said. "That is our job. That is our task. We have to get to work."
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