See Taylor Swift's disgusted reaction to Justin Bieber-Selena Gomez backstage kiss

Justin Bieber was hanging out backstage at the Billboard Music Awards on Sunday when his on-again, off-again flame Selena Gomez walked by with her close friend, Taylor Swift.

In video of the backstage gathering, the 23-year-old Swift looks annoyed when the two stop for a catch-up session, while another friend tries to pull Gomez back into the crowd.

When Gomez wraps her arm around Bieber and grants him a kiss on the cheek, Swift sticks her tongue out.

Here's the GIF, courtesy of Zap2It:

The moment occurs at the 1:00 minute mark below:

Seating arrangements at the musical event fueled speculation that Gomez and Bieber might have rekindled their relationship, though Gomez told a radio station last week that she was "completely available in every way."