WASHINGTON, US - US PRESIDENT Barack Obama will start reversing former President George W. Bush's climate change policies on Monday by taking steps to allow states to limit greenhouse gas emissions from cars and by ordering 2011 vehicle fuel efficiency standards to be set by March.

An administration official said late on Sunday that Mr Obama, who took office last week, would direct the Environmental Protection Agency to reconsider a request by California to impose its own strict limits on car emissions.

The request was denied under the Bush administration. The official said a final decision by the EPA would likely take several months.

California last week asked the new administration to reconsider the state's request.

California and other states sued the EPA after Stephen Johnson, the agency's chief under the Bush administration, denied California's request for federal permission to impose new limits on carbon dioxide emissions from cars.

In a letter to Obama, California Governor Arnold Schwarzenegger asked the president to 'direct the US EPA to act promptly and favorably on California's reconsideration request.

The White House official said Mr Obama would also direct the Department of Transportation to move forward with setting 2011 vehicle fuel efficiency standards by March.

Mr Obama's memorandum would also instruct the agency to reconsider how such standards are set for later years in a separate process.

He promised on the campaign trail to take aggressive action to fight global warming and reduce emissions blamed on heating the earth.

Shortly after his victory in the Nov 4 election, Mr Obama reiterated his commitment to bringing the United States firmly back into the fold of nations trying to reach a global agreement to limit emissions once the first phase of the Kyoto Protocol runs out at the end of 2012. -- REUTERS