Opel's main union says any deal concerning future German pay and conditions is dependent on the automaker's Bochum plant also inking any agreement.

IG Metall cautiously confirms there has been "a step more," in its lengthy Opel negotiations, with the Dudenhofen, Russelsheim and Kaiserslauten plants signing up to an as-yet unspecified deal, but Bochum remains apart.

"We have an agreement with the other plants, but first is the reality if we also have Bochum," an IG Metall spokesman told just-auto from Germany. "We have to wait until negotiations are closed there.

"We need the result for Bochum and this must be decided by the members of the union at Bochum. We are also in negotiation to get a better result, maybe next week or one week later, we will get it.

"I can't give any information because it is not so good for our negotiation if we give this over the newspapers - we need the discussions with General Motors. We will only have agreement if we can get a result for all these plants."

Recent reports indicated unions had agreed a Bochum closure, but not until 2016.