The Obama administration pledged on Monday to stay out of General Motors Co's choice of a buyer for its Opel unit in Europe as German union leaders put more pressure on the U.S. automaker to make a decision.

Negotiations over Opel, which GM is selling as part of a government-orchestrated restructuring, have dragged on for months, frustrating its 50,000 employees.

On Monday, labor leaders for Opel's 25,000 workers in Germany protested the delay by rescinding an agreement to forego their vacation pay, demanding some 70 million euros ($100.1 million) in cash next week, sources familiar with the action told Reuters.

This is the first warning shot, said one of the workers, who requested anonymity.

GM had been expected to reach a decision on Friday on whether to sell Opel to Canadian automotive company Magna International , Berlin's favored bidder, or to Brussels-based bidder RHJ International , but it failed to make a final decision.

GM emerged from bankruptcy protection in July with some $50 billion in U.S. taxpayer loans. The U.S. government has a 60 percent stake in GM, but White House Deputy Press Secretary Bill Burton said on Monday that there were no plans for President Barack Obama to get involved in GM's decision.

The president's view is that decisions made on the day-to-day operations of General Motors should be made by the folks at General Motors. He never wanted to get into the auto business and he's happy for them to make their decisions and get back on their feet, Burton said at a press briefing in Oak Bluffs, Massachusetts, where Obama is vacationing.

An administration official said the U.S. Treasury's autos task force was available to speak with the German government about Opel, but it would not get involved in GM's decision.

The official's comments, made on condition of anonymity because the person was not authorized to speak publicly about the task force, came after German government officials sought U.S. government help in resolving Opel's fate.

German Foreign Minister Frank-Walter Steinmeier discussed the Opel issue with U.S. Secretary of State Hillary Clinton on Saturday, his ministry said.

The ministry added that Clinton had agreed to communicate the German government's position within the U.S. administration.

A U.S. State Department official confirmed that Steinmeier and Clinton had recently discussed Opel, but offered no details.

NO VERDICT FROM BOARD

Despite German pressure for GM to back the Magna bid, which also includes a stake from Russia's Sberbank and a partnership with Russian carmaker GAZ Group , GM's board of directors took no decision on Friday.

The government task force was active in vetting five new GM board members, who were installed in July. None of the board members are government employees.

Instead, the board asked the German government for more information about state financing available for the bid by RHJ, a financial investor, two sources familiar with the meeting said on Friday.

The GM-Opel sale represents an early test of the U.S. government's relationship with an automaker in which it holds majority control. Any U.S. government pressure on GM regarding the Opel decision could cause broader concerns about federal influence in commercial decisions of a range of companies that have received taxpayer support.

'SPECTACULAR MEASURES'

In Germany, the union's action on Monday could be escalated if a decision on Opel does is not made soon. The person familiar with the matter said workers could ultimately demand a 4.2 percent industry wage hike from last year's collective bargaining agreement that they previously agreed to waive for five years.

German Chancellor Angela Merkel, under pressure to find a solution for Opel before a federal election next month, expressed regret over the weekend about GM's delay and said a decision was urgently needed.

Her spokesman, Ulrich Wilhelm, tried to calm the row at a government news conference on Monday, saying it was important that the union not resort to a confrontation with GM.

I can understand that the Opel workers want to have clarity quickly about the way ahead, Wilhelm said. On the other hand, the decision is complex. I think staying calm to preserve a good negotiating climate is in the interest of all sides.

Opel labor leader Klaus Franz, speaking on German radio, threatened spectacular measures if GM did not make up its mind soon. We have been calm so far, listened diligently and made comments, but that is over now, Franz said.

(Reporting by David Lawder and Christiaan Hetzner; Additional reporting by Noah Barkin and Paul Carrel in Berlin, Maria Sheahan and Angelika Gruber in Frankfurt, Arshad Mohammed in Washington, and Patricia Zengerle in Massachusetts; Editing by Patrick Fitzgibbons, Toni Reinhold)

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