Mr Weatherill said that platform would not be dependent to the same degree on fluctuations in the dollar.
Holden managing director Mike Devereux is in Adelaide to tell workers about operations and is expected to release details on Thursday.
Mr Weatherill did not say how many workers would be affected, only that casual and temporary jobs would be "scaled back" over the next few months owing to fewer than anticipated export sales.
There is uncertainty over the car maker's long-term manufacturing future in Australia.
Mr Weatherill said negotiations were taking place between Holden, the South Australian and federal governments on assistance measures.
He said the state government had been told in December that job losses were on the cards, and had argued against them.
"What this demonstrates is the seriousness of the current talks," he said.
Mr Weatherill said SA would do what it could to safeguard the 2000 jobs at Elizabeth and the total 8000 jobs in the industry.
Without change they were not secure, he said.
Mr Weatherill said Holden expected the job losses to come via natural attrition over several months.
The government would support the affected workers where possible, he said.
- AAP