UPDATE 1-Spyker sole remaining bidder for Saab-Whitacre

* Dutch luxury car builder Spyker last Saab bidder

* GM will close Saab if deal not reached by month end

* SAIC deal on China JV set by former CEO Henderson

DETROIT, Dec 15 (Reuters) - General Motors Co [GM.UL] Chairman and acting Chief Executive Ed Whitacre said on Tuesday luxury car maker Spyker SPYKR.AS is the only remaining party with which GM is negotiating for the sale of its Saab brand.

"I think it is possible," Whitacre told reporters in a roundtable discussion at the automaker's board room in its Detroit headquarters when asked if he thought the deal could be completed on Saab by GM's month-end deadline.

Whitacre repeated that barring a deal, GM would close Saab. GM had set an end-of-December deadline to find a buyer for the unit after a deal to sell the brand to sports car maker Koenigsegg collapsed in November.

In his first full question-and-answer session with reporters since becoming acting CEO on Dec. 1, Whitacre also said that GM's deal to sell a majority stake in its China joint venture to partner SAIC was decided before he became CEO.

"It was sort of done before I got here," he said, adding that he had met with SAIC's chief executive in Detroit last week and received assurances at that meeting that the nature of the partnership would not change.

GM's massive restructuring of its operations have included divesting or eliminating the Saab, Hummer, Saturn and Pontiac brands to narrow its focus. In North America GM is now focused on its Chevrolet, Cadillac, Buick and GMC brands.

Whitacre said the board and former CEO Fritz Henderson had disagreed on whether to keep GM's Opel unit. GM reversed a decision to sell a majority stake in Opel, opting to retain and restructure the European unit. (Reporting by Kevin Krolicki, editing by Dave Zimmerman)