FRANKFURT — Daimler and Renault-Nissan significantly expanded their automaking alliance on Friday, saying they would jointly build a production plant in Mexico to build a new generation of compact Mercedes and Infiniti cars.

The companies said they would invest 1 billion euros, or about $1.4 billion, in a plant in Aguascalientes, Mexico, about 300 miles north of Mexico City, where Nissan already has a major production operation.

While the vehicles produced at the 50-50 joint venture will carry different brand names and look different from one another, they will share many components, the companies’ chief executives said in a news conference on Friday.

The companies will also share some of the costs of developing the new vehicles. But they said they were not worried about cannibalizing each other’s sales. There is virtually no overlap between buyers of Mercedes cars from Daimler and Infiniti cars from Renault-Nissan, said Carlos Ghosn, the chief executive of the Renault-Nissan Alliance. “We are not addressing the same customer base,” he said.