Germany’s chancellor decried “unfriendly attacks” on banks after UniCredit moved to raise its stake in the lender.

Italian government officials are growing frustrated at Germany’s opposition to a potential takeover of Commerzbank AG by Milan-based UniCredit Spa, threatening to disrupt the delicate diplomatic relations between Berlin and Rome.

Commerzbank’s management has warned the German government that a potential multibillion-euro merger with UniCredit is a threat to businesses that make up the backbone of Europe’s biggest economy.