Pete Sampras and Roger Federer [Images] attend a joint press conference in South Korean capital Seoul, which will host the first of the three exhibition matches between the two players on Tuesday.

Federer, who retained his Masters Cup title on Sunday, will also take on Sampras in Kuala Lumpur on Thursday and Macau on Saturday.

"I am up against a very big challenge, I've been stepping up my practice," said Sampras, 36, who retired in 2002.

"Perhaps I am not quite as sharp as I used to be, but I think I can still be competitive. But I've got my hands full for sure."

Federer, who is on his way to wipe off Sampras' record of 14 Grand Slams, said "It's a great honour, but not easy at the same time. People will be surprised how well he's actually playing today.

"It's going to be difficult because I practised with him in LA this year.

"He seemed to play very, very well. He's still got the lethal forehand, the great slice and the great serve, you know, the fantastic movement and volleys."

Federer and Sampras met only once in competition, with the Swiss winning a five-set thriller in the fourth round of Wimbledon in 2001.

Photograph: Getty Images