More than 100 banks and credit unions have agreed to offer the person-to-person transfer service being developed by Fiserv Inc.

The Brookfield, Wis., banking technology company said it expects to roll out the service, ZashPay, in early summer, and it expects additional users to sign on throughout the summer.

ZashPay is based on Fiserv's bill-pay service, CheckFree RXP, and will be available initially to all the 3,100 financial companies that use it. Customers of banks that agree to offer it will be able to use ZashPay to send money to anyone, through the recipients' e-mail addresses or mobile phone number. Recipients need not use banks that offer ZashPay to claim their money.

"Consumer interest in person-to-person or social payments is strong, and the network of ZashPay banks and credit unions is growing rapidly," Erich Litch, a Fiserv senior vice president and its general manager for consumer services, said in a press release Wednesday.