By DANA CIMILLUCA

Belgian investment firm RHJ International plans to sweeten its bid for General Motors Co.'s European unit in an effort to overcome German government opposition to its bid.

A deal with Magna and Sberbank poses risks for GM that a deal with RHJ would not. Magna supplies parts to GM rivals and plans to partner with Russian automaker OAO GAZ if it wins the auction. GM is concerned that its intellectual property would leak through Magna.

Magna on Friday said it would create a "firewall" to keep trade secrets of its customers safe should its Opel bid succeed.

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