American Express Company has agreed to acquire German marketing company Loyalty Partner, for approximately $660m.

The credit card company expects to add more than 34 million consumers to its international customer base and expand its range of rewards and loyalty marketing services with this acquisition.

According to American Express, Loyalty Partner will become a subsidiary of American Express and will be part of the company’s International Consumer and Small Business Services group, led by its president, Douglas Buckminster. Alexander Rittweger will continue as CEO of Loyalty Partner.

The purchase, which is subject to regulatory approval, is expected to close in the first quarter of 2011.

Loyalty Partner sells rewards programs to consumers and merchants in Germany, Poland and India. It also offers consulting and analysis programs for merchants.

American Express vice chairman Ed Gilligan said that the loyalty coalition model is growing rapidly in many parts of the world. Increasingly, consumer decisions about where to shop and how to pay are based on loyalty offerings, and Loyalty Partner is a premier player in this space.

"With its state-of-the-art platform, rewards that serve as a virtual currency, outstanding management team, and large customer and partner base, we think Loyalty Partner will be an excellent complement to our existing businesses," Gilligan said.