Ford's chief executive officer Mark Fields has taken aim at President-elect Trump's plan to scuttle free trade and impose a 35% tariff on cars made in Mexico.

"A tariff like that would be imposed on the entire auto sector and that could have a huge impact on the US economy," Fields told Bloomberg after a speech at the AutoMobility conference in Los Angeles. Ford favours "free and fair trade".

Fields reportedly said the automaker has been in touch with Trump's transition team and that he sent a congratulatory letter to the president-elect. The company declined to release the letter, Bloomberg said.

"I continue to be convinced that the right policies will prevail, because I think we all share the same objective, which is a healthy and vibrant US economy," Fields said. "We expect to work very effectively and positively with the president-elect's administration as well as the new Congress."

Fields said he was unsure if Trump would carry through on his threats to terminate trade deals like the North American Free Trade Agreement.

"We'll have to see when President-elect Trump gets into office and the policy he advocates," Fields said in an interview on Bloomberg TV. "We'll engage positively with the administration, talk about policies that will help provide growth here in the US and do our part. But at the same time, make sure that, as a global, successful, multi-national company, that we're building where we're selling."

If Trump institutes a 35% tariff on Mexican-made vehicles "immediately, it will wreak absolute havoc", Rebecca Lindland, senior analyst for Kelley Blue Book, told Bloomberg. "If they have time to plan and rearrange production, it will cause slightly less havoc. But either way, it's going to be very costly for both consumers and businesses."

Trump has criticised Ford for planning to move small car production from a Michigan plant to Mexico but the plant instead will build a new Ranger pickup and revived Bronco sport utility vehicle and Ford has said no jobs will be lost.

According to Bloomberg, Fields said at the conference company officials have talked to Trump's transition team and expect to be able to work with him as president.

"We look forward to working with the new administration and the entire newly elected Congress," Fields said. "We're in constant communication."

Fields reportedly would like Trump to take another look at Obama administration fuel economy regulations originally designed to double average new-vehicle fuel-economy to 54.5 miles per gallon by 2025. Achieving that goal has become more difficult as petrol prices have dropped and consumers have purchased more SUVs and trucks, while turning away from efficient cars and petrol-electric hybrid vehicles, Bloomberg noted.

"We want to make sure that fuel economy regulations are aligned with market realities," Fields said. Ford wants to make sure rules requiring electric and hybrid vehicles match up with "how consumers are reacting to some of the new technologies".