Cleveland Cavaliers' superstar Shaquille O'Neal has issued a challenge to LA Galaxy soccer star David Beckham - to compete in a penalty shoot-out for his television show "Shaq Vs. Show" After his Twitter messages to Beckham went unanswered, however, Shaq claimed that if he is too scared to face him on the field, he should "get a dog!"

O'Neal first proposed the contest on Twitter, stating:

"Dear david beckham, I kno u heard about my shaq vs show, anyway u will never score a goal on me, I challenge you lil man."

A little while later, after having received no reply, Shaq Twittered again:

"Dear david beckham, dnt make me tweet to 2 million people that yur scared of shaq, u betta respnd, if u scared, get a dog."

Still without a response, Shaq posted one final tweet:

"Its official, today is david beckham is scared of shaq, day, he should b scared, he can never score a goal on me."

Perhaps Beckham is just laying low right now. After being on loan to AC Milan, he wasn't exactly greeted warmly when he returned to play with the Galaxy. Beckham also happens to be friends with Kobe Bryant, a former teammate of Shaq's when he was with the LA Lakers. The two fell out while teammates.

In the "Shaq Vs. Show", Shaq takes on top athletes in various sports and tries to beat them at their own game. The show began filming last week, and will premiere Aug. 18 at 9pm ET on ABC. He has already lined up stars like Michael Phelps, Ben Rothlisberger, Oscar De La Hoya, Albert Pujols, Serena Williams, Misty May-Treanor and Kerri Walsh.