The Obama administration, facing political heat over high gasoline prices, may delay new rules that would cut pollution from cars but also could bring higher prices at the pump, environmental and industry leaders said.

The rules would require refiners to make cleaner-burning gasoline and auto makers to build cars that emit fewer smog-forming pollutants. The Environmental Protection Agency was scheduled to roll out the rules before April, but it hasn’t yet submitted them for White House review.

“We expect that timing will begin to slip, perhaps for political considerations” said American Petroleum Institute President Jack Gerard.

The new standards are known as Tier 3, following the Clinton administration’s adoption of Tier 2 standards in 1999.