DETROIT  Automakers said Monday that they were working toward President Obama’s goal of reducing fuel consumption, but rapid imposition of stricter emissions standards could force them to drastically cut production of larger, more profitable vehicles, adding to their financial duress.

Mr. Obama ordered the government on Monday to reconsider whether California and other states could regulate vehicle emissions to help control greenhouse gas emissions, a reversal of a position taken by the Bush administration.

The announcement came as General Motors and Chrysler are borrowing billions of dollars from the government to avoid bankruptcy, and as Toyota prepares to report its first operating loss in 70 years. Shortly after the president spoke, General Motors said it would cut 2,000 jobs at plants in Michigan and Ohio because of slow sales.

The California regulations, if enacted today, “would basically kill the industry,” said David E. Cole, chairman of the Center for Automotive Research, an independent research organization in Ann Arbor, Mich. “It would have a devastating effect on everybody, and not just the domestics.”