• by Laurie Sullivan  @lauriesullivan, February 16, 2012

Twitter will roll out its self-service ad platform to small and mid-size businesses in March through a partnership with American Express. Cardmembers and merchants can register to use the platform and receive $100 in advertising credit to put toward bidding on promoted tweets and promoted accounts.

The service follows a business model that made Google one of the most successful Internet companies through AdSense and AdWords. Twitter said it will allow more merchants to buy ads with American Express in groups of 10,000, at least for the immediate future.

Twitter's advertising revenue grew 213% to nearly $140 million in 2011, up from $45 million in 2010, according to eMarketer. The research firm estimates the company will earn $259.9 million in advertising revenue this year. By 2014, global ad revenues at Twitter are expected to reach $540 million.

The company has been testing and rolling out the platform since last year.