But a California air regulator said the EPA plan "will benefit the climate, air quality, environmental justice, and economic development" and a top environmental group urged the agency to ramp up the pace of adopting electric vehicles to ensure the U.S. is on a path to 100% zero emission new vehicle sales by 2035.

"The stringency of the standards as proposed and illustrated by EPA, are effectively a ban on internal combustion engines," said Bryan Just, a senior policy advisor for vehicles at the American Petroleum Institute.

Just said the rules would "eliminate the opportunity to improve" internal combustion and hybrid technologies "and create an outsized reliance on battery materials from other countries to meet United States' transportation needs."

California Air Resources Board Chair Liane Randolph praised the EPA proposal but urged some changes.

Randolph said "because conventional internal combustion technology will be used for years to come, we encourage you to include mechanisms to ensure that greenhouse gas emissions from those vehicles continue to decline even if the share of ZEVs increases" and called for "stronger provisions for battery warranties."

California needs the EPA's approval for its plan to end the sale of new gasoline-only vehicles by 2035.

Katherine Garcia, director of the Sierra Club's Clean Transportation for All Campaign, said "the EPA must finalize the strongest possible standards this year" and urged the agency to ramp up the pace of EV adoption after 2030.

They testified the second day of the EPA's virtual public hearings on its aggressive proposal for cutting U.S. vehicle emissions for 2027-2032 model years. The plan would require 13% annual average pollution cuts and a 56% reduction in projected fleet average emissions over 2026 requirements.

The EPA estimates the plan would result in 60% of new vehicles by 2030 being electric and 67% by 2032.

President Joe Biden's administration has not endorsed setting a date to phase-out gas-powered vehicle sales.

On Tuesday, the Alliance for Automotive Innovation, representing General Motors, Toyota Motor, Volkswagen AG, Hyundai Motor warned the industry will struggle to meet EPA EV targets because of problems with the EV battery supply chain. Ford Motor separately urged the Biden administration to "harmonize greenhouse gas and fuel economy standards."

(Reporting by David Shepardson; Editing by David Gregorio)

By David Shepardson