The bid would cut Sberbank’s stake in Opel to 27.5 percent from the initial 35 percent, Magna said. Magna would also get 27.5 percent in Opel, up from the original 20 percent, it said.

The rest of the bid appeared to remain the same: Magna, backed by Sberbank, would invest 500 million to 700 million euros in Opel in exchange for the stake and request 4.5 billion euros in loan guarantees from the European governments whose countries have Opel plants.

Calls to a Magna spokeswoman in Canada, Tracy Fuerst, went unanswered late Monday. A Sberbank spokesman declined comment.

Monday was the deadline GM had set for accepting final bids. Magna is competing against Brussels-based investment group RHJ International and China’s Beijing Automotive Industry Holding, both of which submitted a revised proposal, Bloomberg reported. Fiat CEO Sergio Marchionne said it would not improve on a bid that the carmaker had previously submitted.

Magna’s latest bid came after Germen Economy Minister Karl-Theodor zu Guttenberg warned that Opel could be allowed to enter bankruptcy if there were no acceptable bids.

“If everything fails, what we do not want to happen — Opel’s bankruptcy — cannot be ruled out ultimately,” he said in an interview published Sunday in Frankfurter Allgemeine.

German Chancellor Angela Merkel reiterated support for Magna’s bid last week during a visit by President Dmitry Medvedev to Munich.

The new bid by Magna would leave GM as Opel’s majority shareholder with 35 percent. The remaining 10 percent would belong to Opel employees in exchange for their agreement on pay cuts and staff reductions.

GM, which signed a non-binding letter of intent with Magna in May, has been accepting other bids because it is not willing to cede Opel’s intellectual property rights and distribution rights in Russia as Magna demands. Analysts have said that without such concessions, the deal wouldn’t make sense for Magna’s Russian partners, Sberbank and carmaker GAZ.

Magna and its Russian partners will submit its offer as an “ultimatum” and will abandon the talks if the offer is rejected, Kommersant reported Monday, citing an unidentified person familiar with the talks.

While throwing a bone to GM by lowering Sberbank’s possible stake, Magna didn’t back out of its intellectual property demands, the main sticking point.

Without such concessions, the reapportionment of stakes between Sberbank and Magna isn’t a significant change, said Mikhail Pak, an analyst at Metropol.

Another contender, RHJ, is offering 275 million euros ($389 million) in investment for a 50.1 percent stake in Opel. Its plan would require 3.8 billion euros in government guarantees.

Both Magna and RHJ said they would cut about 10,000 jobs at Opel.

Beijing Automotive was offering to invest 660 million euros for 51 percent of Opel and requiring 2.64 billion euros in German government loan guarantees.

General Motors is expected to announce a preliminary analysis of the bids by Wednesday.