U.S. President Barack Obama, flanked by Transportation Secretary Ray LaHood, left, and EPA administrator Lisa Jackson, signs an executive order dealing with energy independence and climate change at the White House on Monday. (Ron Edmonds/Associated Press)

U.S. President Barack Obama said Monday his government will push for allowing states to implement stricter vehicle emissions, a significant shift in policy from the previous administration of George W. Bush.

California and at least a dozen other states have tried to come up with tougher emission standards than those imposed by the federal government but were stymied in their efforts by the Bush administration.

"California has shown bold and bipartisan leadership through its effort to forge 21st-century standards, and over a dozen states have followed its lead, but instead of serving as a partner, Washington stood in their way," Obama told reporters at the White House.

On car emissions, California needed a waiver from the Clean Air Act to pursue its own course; the Bush administration's Environmental Protection Agency denied that permission.

Obama said he will direct EPA regulators to re-examine California's case. The formal process will take time but is expected to end up in the states' favour. The Bush administration had rejected the request on grounds that a national fuel-efficiency strategy would work better.

California Gov. Arnold Schwarzenegger has lobbied Obama to step in and reverse the decision. As a candidate for president, Obama pledged to overturn the EPA's denial.

"By beginning this process and directing EPA to review the Bush administration's lack of action, President Obama is turning the federal government into a force for positive change instead of a roadblock," said the Sierra Club's executive director, Carl Pope.

New auto efficiency standards by 2011

In another key policy announcement, Obama said automakers will have to comply with new fuel efficiency standards by 2011.

Congress has passed legislation that would require new cars and trucks to meet a standard of 6.7 L/100 km (35 miles per U.S. gallon) by 2020, a 40 per cent increase over the status quo. But the Bush administration did not set regulations in support of that law.

"That 40 per cent increase in fuel efficiency for our cars and trucks could save over two million barrels of oil every day, nearly the entire amount of oil [imported] from the Persian Gulf," he said.

"Going forward, my administration will work on a bipartisan basis in Washington and with industry partners across the country to forge a comprehensive approach that makes our economies stronger and our nation more secure."