(Bloomberg) -- Steven Cliff is stepping down as the leader of the US National Highway Traffic Safety Administration less than three months after he officially assumed the role with the auto-safety regulator.

Cliff will become executive officer of the California Air Resources Board as of Sept. 12, according to a statement Friday. The move marks a return to the state agency, where he previously served four years as deputy executive officer.

Cliff was confirmed by the US Senate as NHTSA’s administrator on May 26, making him its first full-time chief since 2017. He had served as the interim head since January 2021.

Ann Carlson, NHTSA’s chief counsel, will take on Cliff’s duties when he steps down, according to a statement from Transportation Secretary Pete Buttigieg. He thanked Cliff for “his work to protect the lives of the American people by strengthening the safety of motor vehicles and reducing their emissions.”

The California regulator has been at the vanguard of clean-air policies for decades, often setting emissions rules that are tougher than federal limits and which are also adopted by other states. Cliff will assume his role after the state board on Aug. 25 considers whether to adopt new rules that will effectively phase out the sale of new internal combustion vehicles in the state by 2035.

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