General Motors Corp. (GMGMQ) could "theoretically" sign a deal with a different bidder for the carmaker's German unit Adam Opel GmbH, government spokesman Thomas Steg said Friday.

But he said: "Negotiations with Magna are at a very advanced stage."

GM is in talks with Austrian-Canadian car parts maker Magna International Inc. (MGA) about an investment in Opel.

The German government said May 30 it selected Magna as a partner for Opel and agreed on providing EUR1.5 billion in bridge financing from the federal and state governments, paving the way for a takeover by Magna and its two Russian partners.

-By Andrea Thomas, Dow Jones Newswires; +49-(0)30-2888-4126; andrea.thomas@dowjones.com