Berlin - The pressure is mounting on giant US carmaker General Motors (GM) Co to decide quickly on the fate of is troubled European Opel offshoot amid signs Monday of increasing tensions between the Detroit-based company and the German Government.

Berlin called for a new round of talks with a General Motors representative in the German capital this week as part of a concerted effort to resolve the future of Opel after the GM board delayed reaching a decision Friday on its European unit.

"The theme cannot be resolved through confrontation, but only between each other," a German government spokesman said Monday with Berlin having also held discussions on Opel over the weekend with the White House and top US Administration officials.

Chancellor Angela Merkel's government has stepped up its calls for GM to end the uncertainty surrounding Opel ahead of a key state poll this weekend and as Germany gears up for a national election set down for September 27.

Opel employs some 25,000 of its total 55,0000 European-strong workforce in Germany and has operations in four of the nation's states, including Thuringia, where a government led by top Merkel ally Premier Dieter Althaus is facing a tough election battle on Sunday.

While Germany's politicians reacted angrily to GM board meeting's move on Friday to postpone reaching a decision on Opel, key union leader at the German Opel operations lashed out the US auto group.

"We have run out of patience," Klaus Franz told Germany's Deutschland radio Monday, adding that Opel employees were now considering industrial action to force GM to settle the future of its European offshoot, which includes the Opel and Vauxhall car brands.

"Everyday day counts for the workers and for the economic situation," said Merkel in a weekend German TV interview.

German Foreign Minister Frank-Walter Steinmeier, who is the standardbearer for the Social Democrats in September election also spoke US Secretary of State Hillary Clinton by telephone on Saturday about Opel.

"Steinmeier stressed that after months of intensive talks, it was time for a decision - and that workers at Opel deserved clarity on the issue, and a real perspective for their future," the German Foreign Office said in a statement.

But while Germany has thrown its support behind a bid led by Canadian-Austrian auto parts group Magna International to buy a majority stake in Opel, German media reports have indicated that some GM officials have begun to question whether the group should give up control of Opel.

This is particularly the case following signs that the global economy is hauling itself out of recession and that government car-buying incentive schemes around the world are boosting car sales.

But the German government spokesman said Monday that Berlin had not seen any signs that the General Motors management might now want to retain Opel.

He went on to add, however, that the decision on selling the controlling stake in Opel was not up to Berlin but lay with GM. Berlin has lent Opel some 1.5 billion euros to stay afloat until a long-term solution to its problems could be found.

In making its bid, Magna International has linked up with the state-controlled Russian savings bank Sberbank and Russian carmaker Gaz. The other Opel bidder is the Brussels-based private equity group RHJ International.

GM had planned to hive off a majority stake in its European operations after slumping sales forced it to embark on a major overhaul of its global business.

But since then, US Administration has installed a new General Motors' board after the American Government took a 60.1-per-cent stake in GM to help it face up to the car industry crisis unleashed by the global recession. (dpa)