General Motors Corp is open to considering moving its headquarters from Detroit, selling off U.S. plants and even renegotiating parts of its restructuring plan with its major union, the new chief executive said on Monday.

CEO Fritz Henderson, on a conference call with reporters, said it was more probable that GM was headed for bankruptcy by June 1 - the U.S. government-imposed deadline for the automaker to restructure or face bankruptcy.

It's more probable that we would need to accomplish our goals in a bankruptcy, Henderson said. There's still a chance for it to be done outside a court proceeding.

A move by GM to leave Detroit would represent another blow for the economy of a region already reeling from the bankruptcy of Chrysler LLC and the sharp downturn in auto manufacturing.

GM purchased its glass-towered headquarter building known as Detroit's Renaissance Center last year for $625 million. The 100-year-old automaker has been based there since 1996.

As we look at the structure, look at the business, we're looking at everything, particularly as we slim, Henderson said. At this point, I don't have anything to report. We don't have any such plans, but if we did it would be motivated by business rationale, which would be cost-efficiency and speed.

GM has until June 1 to reach deals that would slash debt owed to bondholders and the United Auto Workers union and to win concessions from the union that would cut operating costs for its remaining U.S. plants under terms set by the Obama administration's autos task force.

It has already told bondholders that it would miss a June 1 debt payment of $1 billion.

The automaker has also restarted talks with the Canadian Auto Workers union, which just agreed to a set of sweeping concessions for Chrysler, Henderson said.

The UAW, which is crucial to GM's turnaround plans since it is also a major creditor, has raised strong objections to GM plans to increase vehicle imports from plants in Mexico and Korea, saying that runs against the job-saving intent of the U.S. government's support for the automaker.

GM's current restructuring plan, which is supported by the U.S. autos task force headed by former investment banker Steve Rattner, would cut about 21,000 more U.S. factory jobs.

But Henderson said GM was ready to negotiate everything with the UAW in talks now underway. This is something that we would want to have a dialogue with them, he said.

GM shares were trading at $1.45, down 16 cents or 9.94 percent, in late morning trade on the New York Stock Exchange.

(Additional reporting by Poornima Gupta, editing by Leslie Gevirtz)

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