DETROIT — Ford Motor Co. plans to build its new Fiesta subcompact at a factory near Mexico City for sale in the U.S., the company said yesterday.

Ford plans to retool its Cuautitlan Assembly Plant from large-truck to small-car production as it moves to shift its factories from trucks toward more fuel-efficient vehicles, the company said.

The move is a blow to the United Auto Workers union, which last year approved a contract that granted concessions to the automaker. Messages seeking comment were left with UAW spokesman Roger Kerson.

The Fiesta is critical to Ford's effort to unify its global operations and sell versions of the same vehicle in markets worldwide. Three- and five-door hatchback versions will go on sale in Europe this fall and China by the end of the year. Other versions, including a four-door sedan, will reach the rest of Asia by 2009 and North America by 2010. Ford said yesterday that a European hatchback model is being added to the North American lineup.

Ford has sold 12 million Fiestas since the vehicle was introduced in 1976. Although it's a familiar name to customers in Europe, Asia and South America, the Fiesta was only sold in the U.S. from 1978 to 1980.