The Nov.7 failure of the mineral waste storage facility at Tanzania's biggest diamond mine caused flooding in nearby areas, but the company said there were no fatalities or serious injuries.
Petra had initially expected production to be suspended for up to three months.
The London-listed company, which operates three mines in South Africa, said it was reviewing the design of a new tailings storage facility, a process it expects to complete in February 2023.
It would also explore the repair of the existing tailings dam, depending on the outcome of investigations into the cause of the breach.
"As a result of the additional work required to progress these long-term solutions, interim deposition options are being developed that may enable the Williamson mine to resume production around the middle of 2023," Petra said.
Petra, which owns 75% of Williamson, said it was engaging the government of Tanzania, which owns 25% of the diamond mine, on options for financial support to Williamson during the production halt.
The company said this includes the release and sale of a 71,654 carat diamond parcel, which was confiscated by the Tanzanian authorities in 2017 over allegations of undervaluation of gem exports, which the company has denied.
The two parties resolved the dispute in December 2021, when the Tanzania government agreed to release the proceeds of the sale of the diamond parcel to Williamson.
(Reporting by Nelson Banya; Editing by Arun Koyyur)