The union representing workers at First Quantum's copper mine in Panama on Wednesday warned of another union's plan to "invade" the site next week, the latest face-off over the now-shuttered mine that provoked nationwide protests last year.

The UTRAMIPA miners' union said in a statement it was "worried" by the plans of the Suntracs construction workers union, the largest in the country, to force its way into the Canadian miner's operation on January 9.

First Quantum in late November suspended commercial production at the mine and put it into care and maintenance, but the company still has equipment and workers at the site.

Suntracs, which does not represent the mine's workers, in recent months led protests against First Quantum and backed blockades that strangled the mine's ability to bring in supplies.

A Suntracs spokesperson said on Wednesday it would "symbolically close" the mine on January 9, a national holiday commemorating anti-US demonstrations in 1964 over the sovereignty of the Panama Canal zone in which more than 20 Panamanians were killed.

"We're calling all Panamanians to come with us, to go where our sovereignty was violated," Suntracs union leader Saul Mendez said in a press conference late last month.

The miners' union said Suntracs had entered the site by force in 2016 and 2018.

First Quantum did not immediately respond to a request for comment on the plans for the Jan. 9 protests at the mine.

Panama's Supreme Court in late November ruled First Quantum's lucrative contract to operate in the country unconstitutional, prompting the government to order its "definitive" shutdown.

The mine had previously accounted for some 5% of Panama's gross domestic product, but became a flashpoint as previously small anti-mining protests grew into a larger anti-government movement.

The mine's union called for aid from the government in protecting the site, citing previous incidents of violence against workers and the need to avoid an environmental disaster.

Union leader Michael Camacho said that they had yet to receive a response from authorities and that First Quantum had not given instructions to ensure workers' safety.