Federer, the winner of three grand slams this season, and Hewitt will be joined in the Red Group by Spain's Carlos Moya and Argentina's Gaston Gaudio.

Topping the Blue Group will be world number two Andy Roddick of the United States, with in-form Russian Marat Safin, Britain's Tim Henman and Argentina's Guillermo Coria completing the elite eight-player field.

Play in the 4.5 million US dollars tournament begins on Monday and the top two in each group advance to the semi-finals.

Federer has not played since injuring his thigh preparing for his home tournament in Basel last month and he will be relieved tohave avoided Henman, who holds a 6-3 record over the Swiss in head-to-head meetings.