WASHINGTON (Reuters) – Canada and California on Wednesday said they had signed a memorandum of understanding to advance cleaner vehicles and fuels.

The most populous U.S. state and Canada said they will work together “to accelerate the adoption of zero-emission vehicles like electric cars” and share technical information and best practices in regulating cleaner fuels, as California does today though its Low-Carbon Fuel Standard.

The announcement comes as the Trump administration has proposed barring California from regulating vehicle emissions or requiring a rising number of zero emission vehicles.

Canada is reviewing its vehicle emissions standards. The Trump administration in August 2018 after a similar review proposed freezing fuel efficiency requirements at 2020 levels, a rollback of standards announced during the Obama administration.

The administration plans in the coming months to finalize a dramatic rewrite of fuel efficiency standards through 2026 that would also strip California, which wants stricter rules to fight climate change, of the right to set its own, tougher emissions rules.

The Obama-era rules called for a fleetwide fuel efficiency average of 46.7 miles per gallon by 2026, compared with 37 mpg under the Trump administration’s preferred option.

Earlier this month, 17 major automakers including General Motors Co, Volkswagen AG and Toyota Motor Corp urged the White House to resume talks with California to avoid a lengthy legal battle.

On Tuesday, four U.S. House lawmakers led by Representative Debbie Dingell of Michigan again urged California and the Trump administration to meet to try to reach an agreement to maintain nationwide rules.

Canada is working toward having 100% of all light-duty vehicles sold be zero-emissions by 2040. Canada is offering a rebate of up to $5,000 for qualifying zero-emission vehicles and other tax incentives for businesses that want to upgrade to zero-emission fleets.

California allocated $238 million in its 2019 budget for incentives to purchase electric and fuel cell vehicles.

California’s zero emission rules have been adopted by nine other states and Colorado has said it plans to adopt them. The Trump administration would bar the states from requiring them.

California’s Low Carbon Fuel Standard went into effect in 2011 and has displaced 3.3 billion gallons of petroleum-based fuels with low-carbon alternatives including renewable diesel, electricity and renewable natural gas.

Canada is developing a Clean Fuel Standard that will cut emissions by 30 million tons in 2030 – equivalent to taking 7 million cars off the road.