The platform is going live in the US first, as the microblogging site moves to target small and medium businesses to generate fresh revenue streams.
Later today (17 February), American Express cardholders and merchants will be able to register to use the ad platform, to receive a $100 (£63) credit to buy its ad products, which include promoted tweets and accounts.
Twitter rolled out its ad platform in April 2010, and launched the ability to run ads targeting UK users in September 2011. Until now, the ad products have been sold only through a sales team.
It began courting UK brands in September 2010 and opened a London-based office in May 2011. Sky was the first brand to roll out UK-targeted Twitter ads, followed by Electronic Arts and Eurostar.
Twitter has not announced how much its ads cost, as they are bought as packages. However, it recently emerged that some brands have committed to spend at least £25,000 on ads to be able to own one of Twitter's newly launched brand pages.
The move is evidence of Twitter's ambitions to steal share from Google and Facebook, which both offer self-service ads across their products.
Last year, Twitter generated ad revenue of around $140m (£89m), according to research company eMarketer.
Follow Sarah Shearman on Twitter @Shearmans