TORONTO - Canadian miner First Quantum Minerals has opened a voluntary retirement scheme to workers at the Cobre Panama mine, two sources familiar with the matter said, as the company waits for a government decision on restarting the operation.

The mine, one of the world's top sources of copper, was shut down in November, hours after Panama's Supreme Court declared its contract unconstitutional. The decision to close down the mine was also triggered by environmental protests against the operation.

Panama's new government led by President Jose Raul Mulino has said the mine is not on his government's agenda this year and he will take a decision on its future in early 2025.

A significant reduction in the number of workers at the mine could lengthen the time needed to resume production.

First Quantum has asked its employees in Cobre Panama to choose between taking the voluntary retirement offer that would come into effect from January 2025 or work with reduced hours, the sources said.

Employees are expected to make a decision by the end of September, they added on condition of anonymity because they were not authorized to speak publicly about the matter. First Quantum declined to comment.

Michael Camacho, the union leader for Panama Mining Workers Union, said the operation was undertaking a voluntary retirement process and a small number of workers had taken up the offer. He said Panama's government has not indicated what would constitute a safe management plan for the mine.

"There are around 900 people working at the site, down from 6 000 last year and most of the employees would prefer to work with reduced work hours, than take a voluntary retirement", said one of the sources, who did not wish to be identified.

Reuters could not independently verify the number of people currently working at the mine.

Shares of First Quantum closed 0.5% lower on the Toronto Stock Exchange on Monday.

For First Quantum, reopening Cobre Panama mine is essential to managing its debt.

Commodities markets are also watching to see what happens to 130 000 metric tons of copper concentrate that is stuck at Cobre Panama. The Panama government is yet to make a decision on whether it will allow the export of the copper concentrate.