Backstreet Boy Gets Engaged

Credit: Cody Boor/Hard Rock Hotel

Backstreet Boy AJ McLean is making it official.

McLean, 32, proposed to his girlfriend Rochelle Deanna Karidis while performing solo in Las Vegas on Friday night, has learned.

"AJ dropped down to one knee and said that they had been dating for a long time and [he] wanted to know if she would marry him," a source tells Us. "Of course she said 'yes,' and they left the club shortly after this happened."

Another witness tells E! News that the singer bought a "beautiful ring" on the fly at Rocks the Jeweler inside the Hard Rock Hotel before running "back to Wasted Space [to propose on-stage at] the strike of midnight, and the change of the date to Jan. 9 -- his birthday!"

Flip though celebs' personal wedding photos

The club was hosting a party for Web site "Naughty America" to coincide with the AVN Adult Entertainment Expo convention.