WASHINGTON, D.C. — Xerox Corp. and NRG Energy Inc. joined on Wednesday the U.S. Climate Action Partnership (USCAP), bringing total membership to 31.

Xerox's participation marks the first time a high-tech company has entered the ranks of the group, an alliance of business and environmental partners focused on reducing greenhouse gas emissions. NRG Energy, a wholesale power provider, joins others in its industry, such as Duke Energy, Florida Power and Light and Pacific Gas and Electric Co.

"Protecting the environment and implementing sustainable business practices have been priorities at Xerox for decades," said Ursula M. Burns, Xerox president, in a statement. "It makes sense for us to be the first high-tech company to join USCAP, where we can help set goals, priorities and policies that align industries and the government."

The announcement adds to the growing drumbeat urging the federal government to take more aggressive measures to reduce greenhouse gas emissions. On Tuesday, for instance, the Business Roundtable, an association of 160 CEOs, released a policy statement recommending immediate collective action.

NRG's participation in USCAP sends a simple message, said Steve Corneli, who assumed in March NRG's newly created position of vice president of market and climate policy.

"The time to act on climate change is now," he said.

Corneli noted that the U.S. is now the second largest producer of greenhouse gases behind China.

"We don't believe the U.S. can go it alone in making a dent in the climate change issue but we do believe the U.S. can take a leadership role," Corneli said.

NRG also participates in 3C, or Combating Climate Change, a global initiative determined to create market-based solutions to the issue. The company has announced a plan called Repowering NRG that will invest some $16 billion on more than 10,000 megawatts of new, cleaner power plants. Future projects include new wind generation works in California and Texas.

It will file for an operating license with the Nuclear Regulatory Commission this year and intends to build two new nuclear units capable of producing about 2,700 megawatts in South Texas.

It also is developing in western New York an Integrated Gasification Combined Cycle plant with carbon capture and sequestration that can initially capture up to 65 percent of carbon dioxide, with future potential as high as 90 percent.

Xerox plans to cut greenhouse gas emissions from its operations by 10 percent by 2012, it announced in 2005. To do that, it has developed chemical toner that can be produced using up to 25 percent less energy. More than half of its products meet the latest Energy Star requirements. It also has taken strides to boost energy efficiency at its facilities, some of which are powered in part by renewable power.

USCAP companies generate a total revenue of nearly $2 trillion. The organization's principles include accounting for the global dimensions of climate change, creating incentives for technology innovation, being environmentally effective, creating economic advantage, being fair to disproportionally impacted sectors and rewarding early action.