Washington ? President Barack Obama opened an ambitious, double-barreled assault on global warming and U.S. energy woes Monday, moving quickly toward rules requiring cleaner-running cars that guzzle less gas — a must, he said, for “our security, our economy and our planet.”

He also vowed to succeed where a long line of predecessors had failed in slowing U.S. dependence on foreign oil.

Starting his second week in office, Obama took a major step toward allowing California and other states to target greenhouse gases through more stringent auto emission standards, and he ordered new federal rules directing automakers to start making more fuel-efficient cars as required by law.

The auto industry responded warily. Reducing planet-warming emissions is a great idea, carmakers and dealers said, but they expressed deep concern about costly regulations and conflicting state and federal rules at a time when people already are not buying cars. U.S. auto sales plunged 18 percent in 2008.

And industry analysts said the changes could cost consumers thousands of dollars — for smaller, “greener” cars.

Obama on Monday directed the Environmental Protection Agency to review whether California and more than a dozen states should be allowed to impose tougher auto emission standards on carmakers to fight greenhouse gas emissions. The Bush administration had blocked the efforts by the states, which account for about half of the nation’s auto sales.

The new president also said his administration would issue new fuel-efficiency requirements to cover 2011 model year vehicles.

Obama acknowledged the worries of automakers but said urgent action was needed nonetheless. He said, “Our goal is not to further burden an already struggling industry. It is to help America’s automakers prepare for the future.”

He said that U.S. imports of foreign oil have continued to climb, even as previous presidents pledged to reverse the trend. No more, he said.

“I want to be clear from the beginning of this administration that we have made our choice: America will not be held hostage to dwindling resources, hostile regimes and a warming planet,” Obama said in the ornate East Room of the White House, where an audience of environmentalists cheered him on.

Underscoring environmental worries, a new report said many damaging effects of climate change are already all but irreversible, sure to last until the year 3000 and beyond. “It’s not like air pollution where if we turn off a smokestack, in a few days the air is clear,” said Susan Solomon, chief author of the international report and a climate researcher with the National Oceanic and Atmospheric Administration’s Earth System Research Laboratory in Boulder, Colo.