Usher to "shock the world"

Usher's going to duet with Lady GaGa.

He's revealed all in a Tweet, "Yo!..I'm gonna do a record with Lady GaGa that's gonna shock the world!! I just thought of it...Major URIV."

The R&B star has made no secret that he's a major fan of Gaga and always hinted at his desire to collaborate with her.

Usher followed up with another tweet which said, "You gotta think outside of the box, you know. She killin em over here!!"

Usher, who celebrates his birthday on Thursday, has been in London to promote his 2011 OMG tour.