GM has said that it will cut between 9000 and 9500 jobs in Europe - fewer than originally predicted.
However, details of where these cuts will happen, and which plants are under threat, are not expected to be revealed until later today.
So far, it has only been confirmed that Opel's four plants in Germany are safe.
GM's European boss Nick Reilly told the BBC he saw Opel's Eisenach plant as "a significant resource for the production of [Opel] Corsas for the long term".
He had previously given assurances over Germany's three other Opel plants.
"We do need to restructure. We are going to reduce overall European capacity by around 20 per cent and we expect the reduction in head count to be between 9,000 and 9,500 around Europe in total," Reilly said.
He also said GM's European headquarters would be based at Germany's Ruesselsheim plant.