MEXICO CITY (Reuters) - General Motors Co GM.N will gradually restart operations at several idled plants in Mexico beginning this weekend, after unionized workers for the U.S. automaker ratified a new labor contract, the company's Mexican unit said on Friday.

The United Auto Workers (UAW) union announced earlier on Friday that its members had formally approved a new four-year labor contract with General Motors, ending a 40-day strike with the top American automaker.

GM said that by the end of next week all of its Mexican operations should be operating normally with all employees back to work.

In a statement, GM’s Mexican unit said its Ramos Arizpe motors plant will resume operating on Saturday, while its transmissions plant and Chevrolet Blazer assembly line located at the same facility will start back up on Monday. The Ramos Arizpe facility is located in the Mexican border state of Coahuila, just south of Texas.

All of the plants located at GM’s Silao facility, in central Guanajuato state, will restart on Monday.

Thousands of Silao workers had been furloughed as anxiety grew earlier this month among residents who viewed the facility as the city’s economic anchor.

Tensions over the future of manufacturing in North America were at the heart of the striking GM workers. The debate pitted U.S. labor advocates eager to reduce Mexico’s cost advantage against Mexican trade unions fighting to protect local jobs.

The strike began in September with UAW negotiators demanding higher pay for workers, greater job security as well as a bigger share of profits and the protection of healthcare benefits.