WASHINGTON — President Barack Obama ordered federal agencies on Monday to set ambitious goals… WASHINGTON — President Barack Obama ordered federal agencies on Monday to set ambitious goals to reduce greenhouse gas emissions, cut energy use, save water and recycle more, urging a government that once ranked among the nation’s largest polluters to “lead by example” on environmental protection and energy efficiency.

The measures echo a sustainability program launched by the City of Los Angeles under the direction of then-Deputy Mayor Nancy Sutley, who now heads the White House Council on Environmental Quality.

The federal government, which operates 600,000 fleet vehicles, occupies 500,000 buildings and employs 1.8 million workers in civilian jobs, is the nation’s largest energy user. And White House officials said the initiative, which is detailed in an executive order and does not require congressional approval, would yield energy and environmental benefits in its own right and — because of Washington’s huge role as a consumer — encourage added savings throughout the economy.

“The power to do very simple things to conserve energy will do dramatic things to save money,” Sutley said in an interview, adding: “By setting aggressive standards, the federal government helps to move the market.”

No cost estimates were provided, but officials said initial costs — largely to retrofit buildings to make them more energy efficient, would be covered from the stimulus program. Longer term, they said, the program would pay for itself.

The order instructs agencies to set reduction goals within 90 days for the heat-trapping gases scientists blame for global warming. It also calls for a 30 percent cut in fleet petroleum use by 2020, a 50 percent recycling increase by 2015, implementing high-efficiency building codes and adopting a variety of water measures, including cleaning up storm water runoff from government facilities.

Once agencies set their goals and the Council on Environmental Quality approves them, the Office of Management and Budget will publish a “scorecard” of how the agencies are faring.

Sutley said the initiative builds on the experience of Green LA, a 2007 city program that seeks to reduce Los Angeles’ greenhouse gas emissions by 35 percent by 2030, through steps that include strict efficiency standards in building codes and drawing large chunks of city electricity from renewable sources.

Environmental groups say Green LA, despite some struggles, is a good model for a comprehensive federal plan. The city has succeeded in adopting a more efficient vehicle fleet, conserving water and cleaning up ports, said David Pettit, a senior attorney with the Natural Resources Defense Council in Santa Monica, Calif., but is finding more difficulty moving away from coal and planting trees.

John White, director of the California-based Center for Energy Efficiency and Renewable Technologies, said Obama’s push could enjoy greater success based on scale alone. “Clearly, the federal government could do a lot in terms of new, green construction of federal buildings,” he said. “It really helps to have a clear mandate.”