The two companies are piloting the service at the annual South by Southwest Interactive tech-fest that is set to take place in Austin, Texas later this week. Sixty merchants have been lined up to offer a special 'spend $5 save $5' promotion.

The move follows the release last year of a 'social currency' mobile app by American Express that uses the Foursquare system to connect cardholders to their friends for comparison shopping purposes.

Looking to further raise its profile in the social media space, American Express last week posted a job ad for a senior social media manager, to co-ordinate the company's strategy and activities across emerging client engagement channels.