Minneapolis-based U.S. Bancorp on Wednesday announced that its banking subsidiary, U.S. Bank National Association, has agreed to acquire the institutional trust business of Union Bank, N.A, a subsidiary of San Francisco-based UnionBanCal Corporation.

Financial terms of the deal were not disclosed. The trust business that U.S. Bank is buying provides services to retirement plans, labor management trusts, and registered investment advisors. Through the transaction, U.S. Bank will acquire about 4,300 client relationships representing $42 billion in assets under administration.

“This acquisition is a great fit for U.S. Bank and solidifies us as a leading provider of institutional trust and custody services by significantly increasing U.S. Bank's scale supporting the retirement services, labor management, and registered investment advisor markets,” Terrance Dolan, vice chairman of U.S. Bank's wealth management and securities services division, said in a statement.

The deal to buy Union Bank's trust business represents the third acquisition that U.S. Bank has announced during the past week. The bank on Friday said that it acquired Knoxville, Tennessee-based BankEast, which was recently closed by regulators. Then, on Monday, U.S. Bank said that it has agreed to buy the Indianapolis-based corporate trust business of UMB Bank. That transaction is expected to close March 2.

U.S. Bancorp-under which U.S. Bank operates-is Minnesota's largest bank-holding company based on assets, which totaled $316 billion as of June 30.