General Motors chief executive Dan Akerson had said talks with Opel unions about the future of plants there were constructive but would not comment specifically on the future of Bochum.

"We are in discussions with our German unions and others throughout Europe," Akerson told Reuters before GM's annual shareholders meeting. "They're constructive, they're professional, and it's our hope and expectation that we'll come to some sort of mutual understanding."

Akerson would not say of Bochum's future was on the agenda for a GM board meeting later on Tuesday (12 June) but told shareholders actions in Europe would include "removing capacity when and where we can." When asked if talks with unions would cover Bochum's future, Akerson said they related to all GM's European plants.

GM recently said the next generation would be built only in Poland and England, leading to speculation production of the Zafira would move to Russelsheim from Bochum which would be closed. GM has given no assurances for the plant beyond 2014 when present agreements with unions expire.

Akerson told the news agency Europe - where it has lost money in the last 12 years - is the company's most important issue. "We have to fix Europe or at least get it to where it isn't draining the corporate coffers," he said.

Analysts expect GM to reveal more details about its European revivial plan at Opel's 28 June board meeting.

Akerson also told Reuters addressing the company's pension liabilities was key. Earlier this month, the company said it would remove US$26bn, or almost a quarter, of its US pension liabilities by offering pension buyouts to some white collar retirees and shifting responsibility for the plans to a unit of Prudential.

He added GM was not talking to the United Auto Workers (UAW) union about shifting pension liabilities from US hourly retirees to a third party like Prudential but added he was open to that possibility.

"I'm not saying we're going to do it, but it's certainly something that we would consider if the opportunity arose," he said.