ING Group N. V. has agreed to acquire a benefit plan administrator that is jointly owned by Citigroup Inc. and State Street Corp.

ING, Amsterdam, says it will pay $900 million for 100% of CitiStreet L.L.C., Quincy, Mass.

CitiStreet runs a U.S. defined benefit pension business, a U.S. health and welfare business and a retirement services business in Australia.

CitiStreet has about 3,700 employees and $351 billion in assets under management.

ING hopes to close on the CitiStreet deal by Sept. 30.