Twitter said Tuesday it was expanding its advertising program to mobile users, the latest bid by the short-messaging service to boost its money-making efforts.

Twitter said Tuesday it was expanding its advertising program to mobile users, the latest bid by the short-messaging service to boost its money-making efforts.

The San Francisco-based company said users of Apple's and Android devices would begin seeing "Promoted Tweets" in their timelines in the coming weeks.

Promoted tweets are sponsored messages from businesses or others and were introduced two years ago to Twitter.com.

But Twitter users are increasingly accessing the service using and the company is seeking to ramp up its mobile revenue.

Twitter said promoted tweets will appear just once in a timeline on a mobile device and will only be displayed when they are relevant.

"Initially, a small number of users may see Promoted Tweets near the top of their timelines from brands they already follow," Twitter said in a blog post.

Twitter also said that "Promoted Accounts" would feature on the iPhone and on handsets in the list of "Who to Follow" recommendations.

Twitter has enjoyed explosive growth since it was founded in 2006 but it is unclear how successful it has been in translating its popularity into profit.