Justin Timberlake has been challenged to a dance off by his date for the US Marine Corps Ball.

The 'What Goes Around… Comes Around' singer and actor is taking Corporal Kelsey De Santis to ball in Washington tomorrow (12.11.11), and she has warned him he'd better have his dance moves in order.

Kelsey told accesshollywood.com: "My friends keep saying, 'Dance-off!' They know about my skills.

"I honestly don't think he'll be able to keep up with my group of people. I really don't think he'll be able to keep up with us."

Kelsey added her dancing skills include "multiple signature moves," such as "The Dougie."

Justin has recently reunited with Jessica Biel, and while Kelsey is open to a kiss from the star, she insists she won't pressure him.

She added: "I'm single! I don't know if a kiss will happen. I guess that's all up to JT and what his plans are.

"I would never force anything upon him or anything like that!"

Justin accepted an invitation to attend the ball as Kelsey's date after she sent a video asking him online in July. Justin's 'Friends With Benefits' co-star Mila Kunis is also attending the ball as the date of Sergeant Scott Moore.