Ford has taken issue with the new staffing restrictions imposed on factories building car parts in Mexico due to the coronavirus, going as far as calling them “not sustainable”.

Factories in the Mexican state of Chihuahua, where Ford has an engine plant and many auto parts suppliers, are ordered to limit the employee attendance to 50 percent as a measure against the Covid-19 pandemic.

Mexico’s federal government has given automakers, mining firms, and builders the green light to restart work, but some of its states have their own restrictions in place to protect public health.

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Kumar Galhotra, president of Ford’s Americas and International Markets Group, told Reuters that the company had “several suppliers” operating under restrictions in Mexico’s Chihuahua state. “With our U.S. plants running at 100%, that is not sustainable,” Galhotra said in a statement.

“While we do not expect any impact to production next week, we are continuing to work with government officials on ways to safely and constructively resume remaining production,” he added.

U.S. ambassador to Mexico Christopher Landau said that Ford may have to shut down some of its U.S. factories as early as next week if they don’t receive Mexico-made engines. Landau added that a Ford exec told him about the carmaker’s concern over parts produced in the Chihuahua state.

“They’re saying that they’re going to start shutting down factories in the United States as of next week if they don’t get that rolling,” Landau said.

Mexico is home to many automotive factories and suppliers, with many U.S. automakers operating their own facilities there due to the lower labor costs.