All-night talks in Berlin about the future of Opel and Vauxhall have broken down without reaching a decision about who should buy GM's European unit.
Officials blamed the delays on an announcement that Opel would need an extra 300m euros ($US415million) in short-term funding.
The German government wants more information from GM and the US Treasury before choosing a preferred bidder - either Fiat or Magna. Talks will reconvene in Berlin on Friday.
But there are tight deadlines involved, with the sale of GM Europe a key part of General Motors' reorganisation plans.
GM faces a deadline of 1 June deadline from the US government to either restructure its debt or declare bankruptcy.
The German government is particularly concerned about potential job losses, especially because it is an election year, with half of GM Europe's 50,000 workers based in Germany.