Isis has scrapped plans to launch its NFC-based mobile wallet before summer ends next week, delaying the debut of a product designed to provide AT&T, Verizon Wireless and T-Mobile USA with an on-ramp into the potentially lucrative mobile payments space.

"We’re working through a final punch list of things to ensure a great consumer experience and seamless partner integration. The list is short, but a few pieces require additional time," an Isis spokesman said.

An update on "launch specifics and momentum news" will be provided next month, he said. 

Isis was announced almost two years ago as a three-way joint venture between AT&T, Verizon Wireless and T-Mobile. It has yet to go live with its first trials in Salt Lake City and Austin, Texas. 

The company did not provide a reason for the latest delay, but Marketing Director Jaymee Johnson said in an interview with Wireless Week earlier this summer that the deployment wasn't proving to be a simple one. 

“You’re having a multitude of handsets available across multiple operators running different operating systems interfacing with banks… and then you’re making sure that works at hundreds of merchant locations within the market,” he said. “It’s actually a pretty daunting effort to pull off.” 

Isis' system depends on NFC-capable smartphones like Sprint's latest Samsung Galaxy smartphone, the Galaxy Victory 4G LTE. The company did not respond to queries about whether the lack of NFC support in the iPhone 5 had influenced its launch plans. 

Because Isis is partnering with existing payment networks, it won't make money off transactions. Instead, its sales will stem from advertising and fees for carrying banks' cards in its mobile wallet.

Advertising is expected to be a key revenue generator for mobile payment services as marketers look to include loyalty offers and other promotions in payment apps. 

Sprint had initially been interested in Isis, but eventually backed away from the company in favor of Google Wallet. Its Virgin Mobile USA prepaid brand also supports Google Wallet.

Google Wallet has so far struggled to gain traction with consumers, and the lack of compatible handsets and official support from AT&T, Verizon Wireless and T-Mobile has hampered growth.