Brad Pitt has revealed that he started his practical joke war with George Clooney.

Clooney has become well-known for playing pranks on his famous friends. However, Pitt admits that he was responsible for beginning the trend back when the pair were shooting the Ocean's Eleven movie franchise in Italy.

The hunk sent a message to the film crew and pretended it had been written by George.

"I sent a memo to the entire Italian crew, in Italian, that said, 'Dear Crew: We wish you a wonderful shoot. George Clooney asks that, this is a very difficult role for him'," Pitt said in an interview for Bravo's Inside the Actors Studio, which will air in the US on February 10.

"'He needs to concentrate deeply. Mr. Clooney asks that you try not to interrupt him, look him in the eye. If you do need to address Mr. Clooney, please refer to him only as 'Daniel' or 'Mr. Ocean'.'"

Pitt, 48, has revealed that the prank went on for some time, with Clooney playing along as best he could.

"It went on for two weeks," he laughed. "He handled it gracefully, but he was becoming unnerved, I think."

Pitt loves working with Clooney and the pair have become good friends off set as well.

He says the star is great fun to be around and always forms a close bond with cast and crew.

"George is our ambassador on the set. He's fun, he's telling jokes, he keeps everyone together. And he loves that camaraderie. He eats lunch with the crew. There's just no one better at it," Pitt explained.

Clooney, 50, recently revealed he is planning to play an impressive trick on Pitt. However, Pitt insists he also has something up his sleeve.

"I knew that something bad was going to happen by me doing this, so I came up with a second [prank]. Whatever he's got, this is uglier," he added.