American Express and Foursquare announced a partnership on Thursday to provide discounts to AmEx cardholders who use the location-based service to \"check in\" from participating shops and restaurants. AmEx and Foursquare, which announced this week that its membership had topped 10 million, said they were extending nationally a campaign tested earlier this year at the South by Southwest festival in Austin, Texas. AmEx cardholders who link their Foursquare profiles to their cards will get $10 back for spending $75 at clothing store H&M, $20 back for spending $50 at sporting goods store Sports Authority and discounts from restaurants in the Union Square Hospitality Group. AmEx said it will unveil additional offers in the coming weeks. \"The success of our pilot just a few months ago proved that American Express\'s digital capabilities and Foursquare\'s expanding application created something extremely powerful,\" AmEx vice chairman Ed Gilligan said. \"We\'re thrilled to take this partnership to the next level.\" Foursquare chief executive Dennis Crowley said the partnership provides \"millions of American Express merchants with an effortless way to serve up specials to our more than 10 million users.\" Foursquare lets people log their locations by \"checking in\" from where they are at any given moment using smartphones or other Internet-linked devices. Foursquare rewards users with virtual \"badges\" for accomplishments such as traveling to distant places or frequenting boats or trains and some businesses have been offering deals to Foursquare users who check in on their premises.