ST. PETERSBURG, November 10 (RIA Novosti) - Russia's largest retail savings bank Sberbank may sue General Motors for its refusal to sell German automaker Opel despite earlier-reached accords, Sberbank CEO German Gref said on Tuesday.

"We are prepared to defend our position in courts as well. Our lawyers are now studying all possibilities," Gref said, adding, however, that there was still the possibility of agreeing with GM without resorting to courts of law.

The U.S. auto giant decided late on November 3 to retain its big European subsidiary, citing "an improving business environment" in Europe.

On September 10, General Motors announced that it would sell Opel to a consortium of Canada's auto parts maker Magna and Russia's Sberbank. The decision was approved by the Opel board and the German government.

According to the previous plans, the Magna-Sberbank consortium was to have a 55% stake in Opel on a parity basis, and the German carmaker was to control 10%, with GM retaining 35%.