When announced last year, the Biden administration had promoted its plan as an effort to reduce the dependence on foreign oil, help car-owners save on fuel costs and combat pollution.
It was expected to prevent more than 700 million metric tons of carbon dioxide emissions by 2050.
Carmakers were free to use whatever technology they wanted to meet the new standard.
In practice, however, achieving the target was expected to depend heavily on increased sales of electric cars.
That drew pushback from some carmakers, who were already starting to scale back some investments in electric cars in response to uncertain demand.
The big three US carmakers, Stellantis, General Motors and Ford, which are known for sales of bigger cars like trucks and SUVs, have the least fuel efficient fleets in the industry, according to the Environmental Protection Agency.
If electric car sales did not increase enough, General Motors feared it would have to shut down factories making less efficient cars to comply with the Biden-era rules, GM chief executive Mary Barra said at a New York Times event on Wednesday.
The plan is still subject to a formal rule-making process.
Trump said his administration expected the change to help save buyers about $1,000 on the price of a car. The Biden administration had estimated that its rules would save car-owners roughly $600 on fuel over the life of their vehicles.
Kathy Harris, director of clean vehicles at the Natural Resources Defense Council, said the new plan would only benefit the oil industry.
"Gutting fuel economy under the pretense of safety and affordability is a cruel joke for American drivers," she said.