Twitter said on Thursday it would introduce self-serve ads for small- and medium-sized businesses in three countries outside the United States. Businesses in the United Kingdom, Ireland and Canada will be able to buy "promoted" ads that can be shown to targeted Twitter users beginning this week.

Twitter generates the majority of its sales through selling ad packages directly to large companies such as Verizon Communications or Samsung Electronics. But analysts believe it has the potential to greatly boost sales by letting smaller businesses buy automated ads without the help of Twitter salespeople.

Twitter gave U.S. businesses early access to the self-serve program earlier this year.