ReadWriteWeb

American Express has announced today that it invested in the mobile payment startup Payfone, along with others, to close out a $19 million strategic funding round. The two companies have also formed an alliance to create a new global mobile checkout service where Payfone will combine its mobile authorization and payment services with American Express's recently announced digital payments platform Serve.

With Serve, users can send and receive money from their accounts, which are funded by a bank account, a debit or credit card, or by money from another Serve account. Serve will be accepted online, on mobile phones or with merchants who accept American Express cards.

With this new partnership, Payfone will use AmEx's Serve software platform, allowing consumers to purchase both digital and physical goods using their mobile phone number. The move is expected to help strengthen AmEx's position outside the U.S., where typically Visa and MasterCard dominate.

American Express just announced that it plans to acquire Revolution Money for $300 million. The deal is still subject to regulatory approval. Revolution Money, which was founded by AOL's co-founder Steve Case, launched in 2007. The company offers a number of services, including a payment and ATM card that offers discounts at participating retailers and the Revolution Money Exchange, which enables online person-to-person money transactions. It seems reasonable to assume that American Express made this acquisition to get a foothold in the online e-payment market and to challenge eBay's PayPal.