WASHINGTON (Reuters) - Colorado and major automakers said on Monday they have reached a deal on the state’s plan to adopt California’s zero-emission vehicle (ZEV) requirements after earlier talks had ended without a deal.

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The state, which plans to join the California program starting in the 2023 model year, has agreed to allow automakers to earn credits for selling electric vehicles in the two model years prior and use other transitional credits available in other states.

Two major auto trade groups representing 99% of U.S. car and truck sales including General Motors Co GM.N, Volkswagen AG VOWG_p.DE, Toyota Motor Corp 7203.T and Hyundai Motor Co 005380.KS, said the state agreed to address concerns "by providing the support Coloradans need to buy electric vehicles while allowing auto manufacturers to transition into Colorado’s ZEV program."

California has led the way in challenging the Trump administration’s plans to roll back Obama-era environmental regulations. Last week, California struck a deal with four major automakers to tighten emissions rules, bypassing the Trump administration’s effort to strip the state of the right to fight climate change by setting its own standards.

The Colorado agreement must be approved by the state’s Air Quality Control Commission at a meeting later this month.

“This agreement will ensure that Coloradans have access to the range of clean car choices that are increasingly available to consumers in other states,” said Colorado Transportation Department Executive Director Shoshana Lew.

The automakers said Colorado committed to support “the increased adoption and sale of ZEVs, including the state’s commitment to increase the number of ZEVs in its fleet of vehicles.”

In June, Colorado said talks with major automakers had failed to reach a deal on voluntary efforts to boost electric vehicle sales. The automakers explored a deal after meeting with Colorado Governor Jared Polis in April.

Polis in January signed an executive order directing the state to adopt California’s ZEV rules, joining nine other U.S. states: Connecticut, Maine, Maryland, Massachusetts, New Jersey, New York, Oregon, Rhode Island and Vermont.

The California ZEV mandate, first adopted in 1990 and revised on numerous occasions, requires the sale of an increasing number of electric vehicles or other zero-emission vehicles.

Last year, California forecast that about 8% of the state’s new vehicle sales in 2025 will be zero-emission and plug-in electric hybrids.

In August, the Trump administration proposed freezing fuel efficiency standards at 2020 levels through 2026 and barring California from imposing its own vehicle emission rules or setting requirements for zero emission vehicle sales. The administration is expected to finalize that regulation this fall.

California and 18 other states, including Colorado, have said they will fight the Trump administration’s freeze in court, a legal battle that could leave automakers in regulatory limbo for years.