WASHINGTON (AP) — President Barack Obama is planning a major push using executive powers to tackle the pollution blamed for global warming in an effort to make good on promises he made at the start of his second term. "We know we have to do more — and we will do more," Obama said Wednesday in Berlin.

Obama's senior energy and climate adviser, Heather Zichal, said the plan would boost energy efficiency of appliances and buildings, plus expand renewable energy. She also said the Environmental Protection Agency was preparing to use its authority under the Clean Air Act to regulate heat-trapping pollution from coal-fired power plants.

"The EPA has been working very hard on rules that focus specifically on greenhouse gases from the coal sector," Zichal said.

Zichal, speaking at a forum hosted by The New Republic in Washington, said that none of the proposals would require new funding or action from Congress. It has shown no appetite for legislation that would put a price on carbon dioxide after a White House-backed bill to set up a market-based system died in Obama's first term with Democrats in charge.

The plan, with details expected to be made public in coming weeks, comes as Obama has been under increasing pressure from environmental groups and lawmakers from states harmed by Superstorm Sandy to cut pollution from existing power plants, the largest source of climate-altering gases. Several major environmental groups and states have threatened to sue the administration to force cuts to power plant emissions. And just last week, former Vice President Al Gore, a prominent climate activist and fellow Democrat, pointedly called on Obama to go beyond "great words" to "great actions."

It was unclear whether the White House's plans would include controls on existing power plants. An administration official, who wasn't authorized to comment on the plan by name, said the White House was still weighing it. But since the administration has already proposed action on future power plants, the law would likely compel it to eventually tackle the remaining plants, or it would be forced to through litigation.

Obama's remarks in Berlin echoed comments he made in his State of the Union and inaugural speeches this year.

"This is the global threat of our time," Obama said Wednesday. "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. That is our job. That is our task. We have to get to work."

Some environmentalists who cheered those remarks when they were made months ago, criticized them Wednesday.

"President Obama deserves praise for including climate change among the long-term threats facing us all," said Ned Helme, president of the Center for Clear Air Policy, an environmentally friendly think tank. "But he should do more than talk about the problem. The president needs to put the full force of his office behind new regulations that will truly curb greenhouse gas emissions. For too long now, he has produced little action. I'm encouraged that he will finally act and not just ask."

Meanwhile, the environmental community is growing impatient.

"I really can't understand why they haven't moved forward on this more quickly, and we hope that turns around," said Nathan Wilcox of Environment America.

An orchestrated and well-publicized campaign to persuade Obama to reject the Keystone XL oil pipeline, which would carry oil extracted from tar sands in western Canada to refineries along the Texas Gulf Coast, appears to be an uphill battle.

Opponents call the $7 billion project a "carbon bomb" that would carry "dirty oil" and exacerbate global warming. But the State Department in an environmental evaluation concluded that other means of transporting the oil would be worse from a climate perspective.