FRANKFURT (Reuters) - Commerzbank expects Poland’s Supreme Court to rule in August or September on contested Swiss franc loans, its finance chief said, as the bank prepares for heavy writedowns at its Polish mBank subsidiary in the wake of the decision. Once the hit from the ruling is digested, Commerzbank could relaunch a sale of the unit, people close to the matter said. An auction petered out last year after buyers flagged concerns about the possible fallout from the Swiss franc mortgages issue. “mBank is an important part of our strategy and we expect it to continue to contribute to the success of the Group with increasing earnings in the future”, Commerzbank said. mBank had no immediate comment. The Supreme Court is expected to lay out how local courts should treat lawsuits against Polish banks over mortgages customers took out in Swiss francs more than a decade ago to take advantage of low Swiss interest rates, only to face far higher costs when the value of the Polish zloty slumped. While Commerzbank’s supervisory board this week discussed mBank’s future, no decision has been taken and bank will wait for the final ruling before taking any further steps, people close to the matter said. But potential bidders and their advisers are already revisiting mBank in anticipation of a new auction as early as the autumn, other people close to the situation said, adding clarity on the Swiss franc fallout would give them comfort in defining a valuation for Poland’s fifth-largest bank by assets. Commerzbank Chief Financial Officer Bettina Orlopp said at an industry conference on Thursday that after two promising rulings Polish bankers were now more optimistic than a few weeks ago regarding the court ruling. mBank may, however, still face a hit of about 1 billion euros from the ruling, people close to the matter said, adding this was only a rough estimate. Commerzbank has so far set aside 300 million euros in provisions for the case. mBank’s sale was once considered a cornerstone of Commerzbank’s turnaround plans. As Germany’s second-largest listed lender continues to restructure, it would reap proceeds from a sale, but would also be giving up reliable cash cow. Commerzbank is also worried the sale price could be depressed by political interference as Poland’s leaders have said they want more of the country’s lenders in domestic hands. Poland’s ruling nationalist Law and Justice (PiS) party has tightened control over the banking sector and several bidders withdrew from the mBank auction last year confidentially citing political concerns. At the time, a consortium led by PZU and Pekao bid for mBank, while PKO and Erste initially expressed an interest. The banks declined to comment or were not immediately available for comment on Thursday. mBank’s has a market capitalisation of about 12.9 billion zlotys ($3.4 billion). Commerzbank owns a 69% stake. ($1 = 0.8369 euros) ($1 = 3.7907 zlotys) Additional reporting by Agnieszka Barteczko; Editing by Mark Potter Our Standards: The Thomson Reuters Trust Principles.