Nebraska Attorney General Michael Hilgers on Tuesday filed an antitrust lawsuit against some of the largest heavy-duty truck manufacturers accusing them of limiting the availability of diesel-powered semi-trucks in a shift to clean electric trucks.

The lawsuit says the truck makers are engaged in "an industry-wide conspiracy" to phase out medium and heavy-duty internal combustion vehicles, driven by California's green regulations that aim to eventually end production of such semi-trucks.

The attorney general filed suit in state court against Daimler; Navistar, a unit of Volkswagen's Traton; Paccar; Volvo Group North America; and the Truck and Engine Manufacturers Association.

"Eliminating diesel-powered semi-trucks is practically impossible to accomplish and would impose enormous costs," Hilgers said. "These manufacturers' collusion will raise prices, reduce output, increase costs on Nebraskans, and is a classic antitrust violation."

The lawsuit takes aim at a July 2023 deal reached between California Air Resources Board and major truck manufacturers and the Truck and Engine Manufacturers Association that gave the industry flexibility to meet emissions requirements.

The companies agreed to meet California's vehicle standards "regardless of whether any other entity challenges California's authority to set more stringent emissions standards," CARB said at the time.

CARB and Paccar declined to comment. The other companies and the association did not immediately comment.

In March 2023, the U.S. Environmental Protection Agency approved California's plans to require a rising number of zero-emission heavy-duty trucks. California is still awaiting EPA approval for its Advanced Clean Fleets regulations on phasing in use of zero emission medium-duty and heavy-duty vehicles, and light-duty package delivery vehicles. The rule would require manufacturers to only manufacture ZEV medium- and heavy-duty trucks starting in 2036.

In May, Nebraska and 15 other states sued CARB over its clean fleets rule.

California Governor Gavin Newsom said last year that half of all heavy duty trucks sold in California will be electric by 2035. The state plans to mandate by 2045 that all operations of medium- and heavy-duty vehicles be zero emission where feasible.