Serbian Novak Djokovic plays Argentine Juan Martin del Potro and Russia's Nikolay Davydenko meets Jo-Wilfried Tsonga of France in opening-day matches.
Defending champion Roger Federer, who has won the event the past two years and four times overall, is set to begin defense of his title in a match Monday, against Frenchman Gilles Simon.
Federer defeated Spaniard David Ferrer in the championship match last year.
In another Monday match, Britain's Andy Murray goes against American Andy Roddick.
The tournament uses a round-robin format with a four-player Red Group (Federer, Murray, Roddick and Simon) and a four-player Blue Group (Djokovic, Davydenko, Tsonga and del Potro).
Federer became the top seed when world No. 1 Rafael Nadal withdrew because of a knee injury.
The tournament will be played in London in 2009.