WASHINGTON - U.S. President Barack Obama ordered federal agencies on Monday to set a goal within 90 days for cutting their greenhouse gas emissions by 2020, the White House said, aiming to lead by example in fighting climate change.

The new executive order, signed by the president, mandates agencies across the federal government to measure, manage, and reduce greenhouse gas emissions toward agency-defined targets, the White House said in a statement.

Other environmental measures such as reducing petroleum use in vehicle fleets by 30 percent by 2020, improving efficiency f water usage by 2020, and increasing rates of recycling by 2015 were also included in the order.

The federal government can and should lead by example when it comes to creating innovative ways to reduce greenhouse gas emissions, increase energy efficiency, conserve water, reduce waste, and use environmentally-responsible products and technologies, Obama said in a statement.

Obama's international credentials on fighting climate change have been called into question as chances dim that the Senate will pass a bill mandating emissions cuts across the United States economy by December, when U.N. talks on a global warming treaty take place in Copenhagen.

The White House order may be intended to counter concerns about the president's climate change commitment.

The federal government is the largest consumer of energy in the U.S. economy, the statement noted, occupying nearly 500,000 buildings and operating more than 600,000 vehicles.

The order also calls on the government to leverage federal purchasing power to promote environmentally-responsible products and technologies.

(Reporting by Jeff Mason; Editing by Eric Walsh)