Mizuho Financial Group Inc. will join two U.S. banks in partly financing a $66 billion acquisition in the U.S. pharmaceutical industry, its president said recently, describing the move as the banking group's leap into the deal business.

Mizuho, Japan's second-largest lender by assets, will extend a $45 billion bridge loan together with JPMorgan Chase & Co. and Wells Fargo & Co. to help the purchase by specialty pharmaceutical company Actavis PLC of its peer Alergan Inc.

Mizuho is set to provide about ¥1.8 trillion ($14.8 billion).