UniCredit said it converted part of its position in peer Commerzbank into stock to double its equity stake, becoming the largest shareholder of the German lender that it hopes to engineer a merger with.

The Italian bank said late Tuesday that it now owns around 20% of Commerzbank’s shares and effective voting rights after the conversion of a 10% interest it previously held in derivatives. The transaction follows approvals from the European Central Bank, German antitrust regulator and the Federal Reserve, it said.