American Express' new digital payments platform Serve has just announced its second operator partnership here in the U.S. will be with Verizon Wireless. This news follows last month's report that Sprint would also integrate the Serve platform into select Android phones on its network.

According to Verizon, its customers will be able to sign up for Serve accounts on both Verizon phones and tablets, although it did not specify which devices those would be.

Serve, which can be funded by a bank account, debit or credit card, or from another Serve account, does not require users to be American Express card holders. Instead, it's aimed at those who don't rely on credit cards. With Serve, customers can shop both online and offline, anywhere American Express is accepted.

Verizon Wireless customers will be able to use Serve to buys goods and services on their mobile device in just a few clicks. The process is easier than entering in a credit card number by hand, because all that's required to checkout using Serve is your mobile phone number.

American Express and Verizon will also team up to use Serve as a way to source, distribute and enable the redemption of online and mobile offers with participating Serve merchants. The offers and coupons customers redeem at checkout will automatically appear in their Serve accounts, which can be viewed and managed online and on mobile.

In addition, both companies are working with Payfone, a mobile payments startup which American Express invested in this spring.  Payfone helps to combine mobile authorization and payment services with the Serve platform. This allows customers to pay for both digital and physical goods using just their phone number. Payfone is unique as it leverages the security built into mobile operator networks to fight fraud. With Payfone, the customer's SIM card, device ID and location are tied to each customer's account for more secure transactions.

Merchants interested in learning more about accepting Serve can visit www.serve.com/billmyphone.