FleetBoston

(FBF)

said Friday that it sued to block

Advanta's

(ADVNB)

proposed sale of its mortgage business to a unit of

J.P. Morgan Chase

(JPM) - Get Report

.

FleetBoston said it wants the transaction blocked unless Chase assumes the alleged $140 million obligation Advanta has to Fleet. Representatives of Advanta weren't immediately available for comment.

FleetBoston contends that the sale of Advanta's assets meets a provision of its 1998 agreement to buy Advanta's credit card business. FleetBoston said that the buyer of "substantially all" of the rest of Advanta's assets is responsible for any remaining obligations tied to the transaction.

Advanta said in October that it planned to sell its mortgage business, and in January, the company agreed to sell the operation to

Chase Manhattan Mortgage

, a unit of J.P. Morgan Chase, for an estimated $1.6 billion.