MILAN/FRANKFURT, March 16 (Reuters) - Italy's UniCredit said on Monday it was launching an unsolicited offer to increase its stake in Commerzbank to more than 30% and push its rival to engage in merger talks. 

While UniCredit said it did not expect to achieve control of the German lender, in which it already holds a 26% equity stake and another 4% through total return swap contracts, the move ramps up pressure on Commerzbank's management after a pursuit that started more than a year ago. 

"UniCredit signals openness for dialogue and willingness to build bridges with Commerzbank and key stakeholders," the Italian bank said in a statement.

UniCredit has met strong German opposition to a full takeover of Commerzbank following its initial investments, and CEO Andrea Orcel repeatedly said he would only launch such a move if all stakeholders were supportive.

"It is expected that UniCredit will achieve a stake in Commerzbank in excess of 30% without reaching control," UniCredit said.

"The offer is designed to overcome the 30% cliff-edge that exists under German takeover law and foster constructive engagement with Commerzbank and its stakeholders in the coming weeks," it added.

Under German rules, the markets authority will determine the price of the offer, UniCredit said, adding it expected it to be set at 0.485 of a UniCredit share for each share of Commerzbank. That would imply a price of 30.8 euros per Commerzbank share, or a 4% premium on the German bank's closing price on March 13.