Unionized workers at Chile's Codelco, the world's largest copper producer, have begun a 24-hour strike in a dispute with the government over the future of the company.

The workers walked off the job Monday over modernization plans that union officials say will lead to huge job losses and possible privatization of some of the company's plants. Codelco officials say the plants will not be privatized.

This work stoppage is Codelco's first in nearly 20 years. Codelco says the strike would halt production of about 4,900 tons of copper and generate losses of more than $40 million. Codelco produces 9 percent of the world's copper, or about 1.7 million tons per year.

The strike coincides with the 40th anniversary of Chile's nationalization of the mining industry, a move by then-President Salvador Allende. The nationalization of the mines led to the creation of Codelco.