In the draft, the agencies lay out eight different options for revising the Obama-era standards. The preferred course of action would freeze fuel-economy standards at 2020 levels for both cars and light trucks, greatly slowing progress in reducing auto emissions.

The proposal also challenges California’s authority to impose its own vehicle standards.

Currently, California has a waiver under the Clean Air Act to impose its own, stricter, air pollution regulations on cars and trucks to deal with problems like smog. But the administration’s draft proposal argues that California cannot use this waiver to set standards on greenhouse gas emissions from vehicles because that would be tantamount to regulating fuel economy, which states are forbidden from doing under a 1975 law.

The auto industry has previously tried to challenge California’s greenhouse gas standards for vehicles on these grounds, but federal courts have so far rejected their arguments. Legal experts have said that, as long as California is regulating the pollutants that come out of tailpipes and not directly determining fuel economy standards, the state is on solid legal ground.

The Trump administration has also signaled that it would consider rescinding California’s waiver altogether, although the draft proposal does not mention this. On Thursday, Mr. Pruitt told Congress that the agency was still in “active discussions” with California and had no plans at the present to revoke the waiver.

In recent months, automakers have become increasingly nervous about the Trump administration’s collision course with California. A group of automakers has requested a direct meeting with President Trump to urge the administration to avert a legal clash with California, which could plunge the auto industry into regulatory chaos, according to two people with knowledge of the automakers’ plans. A spokeswoman for the Alliance of Automobile Manufacturers was not immediately available for comment.