Freeport McMoRan Copper & Gold will slightly cut copper ore production at the world’s No.5 copper mine in Indonesia from Monday, according to an internal company memo, due to scheduled maintenance and uncertainty over new export rules.

Freeport has halted concentrate exports from its Grasberg complex in Papua since Dec. 15, and has yet to resume shipments as it waits for clarity on Indonesia’s controversial ore ban and export tax that came into effect on Sunday.

Freeport and fellow copper miner Newmont Mining are expected to meet with finance ministry officials on Friday.

"A previously scheduled maintenance period at the Gresik smelter and the uncertainty associated with new GoI [government of Indonesia] regulations related to exports require that we adjust our near-term operating plans,” the US mining giant said in an internal memo obtained by Reuters. "The Big Gossan Mine will stop all ore production.”

The Big Gossan underground mine accounted for about 1 percent of the Grasberg complex’s output, or 2,000 tonnes per day, in the nine months ended Sept. 30, 2013, according to the Freeport website. Total production at Grasberg open pit and DOZ mine will not be affected, the memo added.

Grasberg open pit produced 122,700 tonnes per day during the same period, with the DOZ underground mine output at 45,900 tonnes per day, according to the firm’s third-quarter results.