NFC-based mobile payment systems have escaped mainstream consumer acceptance (or availability, for that matter) in America so far, despite the fact that trials have been running in places like San Francisco and New York for several years. The ISIS initiative -- announced late last year by partners AT&T, Verizon, and T-Mobile -- seeks to take a broader, standards-based stab at taking mobile payments mainstream, but it's actually Google that might end up playing a bigger role.

Coincidentally, Google's Nexus S launched right around the same time that ISIS was announced, becoming the first broadly-available smartphone in the US with NFC capability built in -- and, perhaps more importantly, easily accessible by any developer that wanted to interact with it. Thing is, Google isn't involved with ISIS... and by all appearances, it doesn't intend to be for the moment.

Bloomberg is reporting today (from three sources, no less) that Google intends to announce a mobile payment service this Thursday at an event in New York City to be offered first on Sprint's WiMAX-capable Nexus S 4G. That makes sense considering that Sprint is the only carrier of the country's big four not participating in ISIS, and it also dovetails nicely with the fact that Google's already been working closely with Sprint in recent months (on Google Voice integration). Previous rumors have Google's launch pegged for rollouts in New York, Los Angeles, Chicago, San Francisco, and Washington, DC, which all have population densities high enough to give a service like this some critical mass to work with.

If anyone has the mojo to give NFC payment services the kickstart they desperately need, Google does -- but they'll need to rapidly broaden the hardware portfolio and add additional carrier partnerships, because no single phone or single network can take the concept to the next level. How ISIS might contribute to the conversation remains to be seen, but a marriage between their efforts and Google's would certainly seem like a step in the right direction.

[Via Phone Scoop]

Update: And we've just gotten an invite for a Google event in New York on Thursday, so the stars are aligning. We'll be reporting live -- stay tuned!