Twitter is testing out a new ad scheme that would allow brands to leverage both user tweets and their own through a carousel format.

One caveat, though, is brands will need explicit permission from users to promote their tweet as an ad.

Reports of the new format first surfaced at CES this year, but now it's got an official name. Dubbed Promoted Tweet Carousel, it allows brands to curate multiple tweets within a single, swipeable ad unit that can include videos, images or text. Brands can also combine content from niche creators or users, the company said.

Twitter claims user tweets provide brands with an authentic form of advertising and shave down costs for advertisers as they don't have to build additional creative. Advertisers are charged based on the number of engagements an ad unit receives, Twitter said.

Although the service is only in limited testing to select accounts, companies like Volvo and Disney have already begun using Promoted Tweet Carousel, the company said.

Disney, for example, pulled tweets from its own handle and users to promote its movie "The BFG," Twitter said. Volvo, meanwhile, said it uses Twitter's ad carousel to show multiple videos within an ad unit.

The company does not have a system in place for brands to give users money for their tweets, but a spokesman said the two could figure that part out on their own.

"Advertisers have told us that creating compelling, engaging content can be both expensive and time-consuming," Andrew Bragdon, revenue product manager at Twitter, said in a statement. "We also know that driving word of mouth marketing is critical as marketers want to develop an authentic relationship with customers. Since people Tweet about their favorite brands and products every day, we developed this powerful solution to help marketers leverage social recommendations."