The company announced the plant in the San Luis Potosi state today without saying specifically what cars it will build there.
But the United Auto Workers union has said Ford plans to shift production of the Focus compact and C-Max small gas-electric hybrid from suburban Detroit to Mexico, where the cars can be made cheaper and more profitably.
Union members have said they expect the factory to get a new version of the Ranger small pickup and a new small truck-based SUV called the Bronco.
Ford announced the move on the day of the key Wisconsin primary.
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Outsourcing jobs has been become a campaign issue largely because of Republican front-runner Donald Trump, who has railed about corporate America moving jobs to Mexico to take advantage of what he calls a lopsided trade agreement.
Auto and other manufacturing jobs having been moving south for years.
Mexican auto production more than doubled in the past decade, and the consulting firm IHS Automotive expects it to rise another 50 per cent to just under 5 million by 2022.
US production is expected to increase only 3 per cent, to 12.2 million vehicles, in the next 7 years.
Joe Hinrichs, Ford's president of the Americas, said Ford is a global automotive company that builds cars where it makes the most sense for the business.
"We've talked about improving our small-car profitability and this is an important part of that," he said today in an interview with The Associated Press.
Trump began criticizing Ford since last summer after the company said it planned to invest USD 2.5 billion in engine and transmission plants in Mexico.
Hinrichs said the timing of the plant announcement had nothing to do with the presidential race, but instead with the timing of construction, due to start this summer.