WASHINGTON (Reuters) - President Barack Obama is likely to roll out a number of measures on climate policy, potentially including a strategy to limit greenhouse gas emissions from existing power plants, in a speech on Tuesday, sources familiar with the plans told Reuters.

The potential move on power utilities, which account for roughly 40 percent of the nation's carbon dioxide emissions, will come as Obama sets the fight to curb climate change as a priority for his second term.

Regulations are still pending on yet-to-be-built power plants, after the Environmental Protection Agency in April missed a deadline to roll out emissions rules.

But environmentalists have been pushing the administration to go after a bigger target, and set tighter standards for the roughly 1,400 coal-fired burners that are already feeding the nation's electric grid.

Earlier this week, the White House's top energy and climate adviser, Heather Zichal, said that Obama will take several steps to make tackling climate change a "second-term priority".

"In the near term, we are very much focused on the power plant piece of the equation," she said at an energy and environment forum.

Besides framing power plant emissions in the context of climate change, many of the steps outlined by Obama to curb demand for carbon-based fuels are likely to be modest.

The president is likely to talk about the importance of conserving energy, for example.

On Wednesday in Berlin, Obama said the United States understood it had to do more to fight climate change and he pledged that more action was coming.

"Our dangerous carbon emissions have come down, but we know we have to do more. And we will do more," he said in a speech.

Controlling carbon dioxide, a byproduct of burning coal and other fossil fuels, is seen as a vital step in confronting climate change.

"The president has telegraphed very clearly that he intends to continue progress on this issue," said White House spokesman Jay Carney, who declined to comment on whether an announcement would come next week.

The timing of the announcement may yet be delayed, sources said. Obama is scheduled to fly to Africa on Wednesday.

Earlier this week, several environmental groups said that they would delay planned lawsuits against the EPA for failing to set standard for new power plants, as they await the White House's proposals.

"We're hopeful the President will announce common sense action to protect our economy and the health of all Americans from the very real threat of climate change," said Fredd Krupp, president of the Environmental Defense Fund.

On Wednesday, Zichal said the administration plans to expand energy efficiency standards for appliances and accelerate clean energy development on public lands. Other elements might include raising onshore oil and gas royalties, which was suggested by the administration earlier this year.

(Reporting by Patrick Rucker, Valerie Volcovici and Jeff Mason in Washington, additional reporting by Scott DiSavino in New York; Editing by Marguerita Choy)