Managing director Julian Ford said he expected the production cash-cost estimate to be included in the plan, which was expected to be finalised next month.

Speaking at the Resources Rising Stars conference on the Gold Coast, Ford acknowledged that the sharp fall in the gold price had triggered a need to revise the mine plan.

"It's taking a few months longer than I had hoped but we should have the mine plan finished by November 4," he said.

The plan hinges on a switch in the starter pit at Tembang from the relatively low-grade Asmar deposit to the higher-grade Buluh pit.

Sumatra needs the mine plan to finalise a debt package that was initially negotiated with the Swiss investment vehicle Credit Suisse in February - two months before the gold price fell sharply.

The lower gold price forced Sumatra to update its mineral resource estimates via additional drilling and to revise its mine development plan to bring forward production of higher-grade material.

In a report to the Australian Securities Exchange two weeks ago Sumatra said project expenditure would be slowed pending the finalisation of the debt and equity funding package.