SA’s Liberal Government is trying to claw back over $291 million offered to Nyrstar by the former Labor government.

Treasurer Rob Lucas is engaging in formal negotiations with Port Pirie lead smelter operator Nyrstar's international CEO, Hilmar Rode.

The former Labor government underwrote nearly half of the $660 million redevelopment of the Port Pirie smelter.

Nyrstar missed its first scheduled $21 million government repayment in May, and has since faced intense criticism from unions over allegedly breaching a bargaining agreement.

Mr Lucas said the negotiations would focus on two key objectives.

“We want to see the success of the Nyrstar redevelopment [including] the protection of as many jobs as we can and successful environmental outcomes as well from the project,” he said.

“It's also absolutely critical that the interests of the taxpayer are protected and they're not placed at any greater risk over the coming weeks.

“It won't be resolved tomorrow, it will be resolved over a number of weeks with lawyers on both sides, lawyers at 40 paces in terms of negotiating what will hopefully be a productive commercial settlement in relation to all of this.”

The Treasurer said any deal is still a while off.

“If it's done before early next year that would be terrific,” he said.

“But if it was to be early next year, where there was a resolution which protects the interests of taxpayers but also ensures the ongoing development of Port Pirie and hopefully the ongoing viability of Nyrstar globally then waiting for that period of time will be time well spent.”