Twitter has begun promoting tweets, in your Twitter timeline.

The next phase Twitter's "Promoted Tweets" program is to bring promoted tweets - Twitter's version of ads - into the Twitter user timeline via a test using Hootsuite, Twitter said Monday.

"When we launched Promoted Tweets in April, we outlined our plan for gradually rolling them out in all of the places people experience Twitter: first in search on Twitter.com, later in search through our partners, and eventually in the user timeline," spokesman Matt Groves noted in a blog post.

In May, Twitter's then chief operating officer, Dick Costolo, said that the site would have hundreds of advertisers by the fourth quarter. Costolo ascended to the CEO position after Ev Williams stepped down in October.

Will users react positively to ads? Grooves said that the site is taking a "softly, softly" approach. "As we have done since the beginning of our Promoted product efforts, Twitter is taking a deliberate and thoughtful approach to this test. We're carefully looking at how Twitter users react to and engage with Promoted Tweets in the timeline. We want to display Promoted Tweets in a way that's both useful and authentic to the Twitter experience."

Not all Twitter users will see the promoted tweets, and Twitter will display the ads only to those users where the tweets are "relevant," Grooves said. "We will expand the rollout only when we feel we're delivering a high-quality user experience," he wrote.

Twitter already launched "Promoted Accounts" in September, in another bid for revenue.