US carrier Sprint Nextel has signed an agreement with American Express which will enable some of its smartphone users to access the credit card giant’s recently-launched mobile-payment service called Serve. This is the first agreement Amex has reached with a mobile operator to support Serve since its launch in late March this year. Sprint customers with Android handsets will be able to download a Serve app which will enable them to make purchases at participating merchants and pay their Sprint mobile bills. The app will become available later this summer. In the future, Sprint customers will also be able to redeem offers on goods and services. However, the Amex app is not available for download to two Android handsets: the Nexus S 4G and Samsung Moment.  The former is used by Sprint Nextel to offer the rival Google Wallet m-payment service.

Perhaps it is not so surprising that Amex should strike its first operator deal to support Serve with Sprint Nextel. After all, Amex’s drive into mobile is headed by Dan Schulman (pictured) who was hired last year from the same mobile operator where he headed the pre-paid business.  The credit card company aims to expand its mobile strategy so that Serve supports a greater number of smartphone operating systems in the future. Serve apps are currently available for Apple’s iOS, as well as Android. Amex wants to expand that list to include the RIM BlackBerry and Microsoft Windows Phone 7 OS. For its part, Sprint Nextel is also filling out its own strategy by signing up to Serve. In addition to joining forces with Amex, it was also the first operator to back Google Wallet, plans for which were announced earlier this year.