U.S. officials must show greater cooperation and seriousness in the debate about the future of General Motors Corp.'s (GM) Adam Opel GmbH unit, German Economics Minister Karl-Theodor zu Guttenberg said Thursday.

"What happened overnight in part borders on the absurd," he told reporters on his way to a budget committee meeting.

"I would hope for more seriousness and willingness to compromise from the U.S. side," Guttenberg said.

Germany in the early hours of Thursday delayed a decision on providing state-backed bridge financing to Opel because the U.S. parent company has come up with new cash demands.

Germany's government won't be a pushover in negotiations over Opel's future, Guttenberg later told the budget committee.

GM Wednesday presented a new surprise cash demand of EUR300 million, which the federal government is unwilling to meet.

Finance Minister Peer Steinbrueck, also present at the budget committee meeting, said the U.S. approach to the debate "has not been transparent."

-By Beate Preuschoff and Nina Koeppen, Dow Jones Newswires; +49 (0)30 - 2888 4122; beate.preuschoff@dowjones.com