Isis, the US mobile wallet venture set up by AT&T Mobility, T-Mobile US and Verizon Wireless, has announced plans for a nationwide rollout later this year.

The partnership between three of the top four US operators enables subscribers to make payments, collect loyalty points and redeem coupons using NFC-based smartphones at the point-of-sale.

Isis has been trialling the wallet in Austin, Texas and Salt Lake City, Utah since October last year.

The trial was originally planned for earlier in 2012 but suffered from delays.

One of the key factors that will determine Isis’ take-up at the nationwide level is device availability. To this end, the venture says nearly 20 million smartphones in circulation feature NFC. And millions more NFC handsets are being shipped each month by the three operators behind Isis, it says.

A total of 35 NFC models across the three operators’ device portfolio currently support the Isis wallet, and that number will grow, it says. The announcement does not specify but these devices are likely based on Android.

The venture says Isis support for iPhone, Windows Phone and BlackBerry 10 is expected later this year. The comment about iPhone is interesting since Apple has famously not adopted NFC. Isis offers no further detail.

However, Isis has worked with DeviceFidelity, a vendor that has developed a NFC-enabled case that can be attached to iPhones.

Adoption by retailers will also influence Isis’s take-up. Twenty five of the top 100 national retailers in the US have either deployed or are deploying the contactless terminals needed to accept mobile payments, says the venture.

“As part of our commitment to consumers, we are incorporating feedback from our pilots into the next generation of the Isis Mobile Wallet as we prepare for national availability later this year,” said Michael Abbott, Isis CEO (pictured).

To access the wallet, mobile subscribers need an secure, NFC-enabled SIM as well as smartphone.