The plant stopped production after the Swiss company filed for bankruptcy. "I'm ready, under certain conditions, to make an offer and save jobs," the US national told AFP. The Klesch group, which is based in Geneva, London and Moscow, invests in metals and mining, oil and gas, power generation and chemicals. On investing in Petit-Couronne Klesch said: "To be clear, it's challenging. It's a company which has been under-invested for over 10 years. "At the end of the day, under certain conditions, I would be prepared to buy Petit-Couronne, investing in it." "If the unions do not want me, I will invest my money elsewhere," he added. Petroplus said Friday that the subsidiaries which run its Swiss and Belgian refineries had filed for protection from creditors. Petroplus Tankstorage AG and Petroplus Refining Cressier SA, which owns the Cressier plant in the Neuchatel canton, have filed for protection from creditors, the company said in a statement. Another subsidiary, the Belgian Refining Corporation NV, which owns Petroplus' Antwerp refinery, had also filed for protection, it said. The company further announced that a request for protection filed earlier this week for Swiss subsidiary Petroplus Marketing AG had been granted. Petroplus, with $1.75 billion (1.3 billion euros) in outstanding debt, was forced to act after the failure of talks with lenders to reopen vital credit lines.