A merger of the German public-sector banking giant WestLB with its shareholding savings banks or "Sparkassen" would not be desirable, WestLB chairman Thomas Fischer said on Thursday. "I wouldn't risk it," Fischer told a banking congress. Analysts have repeatedly speculated about a possible tie-up between WestLB and the large publicly-owned Sparkassen of North Rhine-Westphalia, which own the majority stake in WestLB. But while he ruled out vertical integration with the Sparkassen, Fischer said he favored cooperation with private-sector banks. The divisions between the public, private and cooperative banks in Germany were not so strict as they were in the past, Fischer said.