Chelsea's Salomon Kalou, Real Madrid's Royston Drenthe and Liverpool's Ryan Babel will add star quality to the pre-Olympic tournament in Hong Kong. The US have been confirmed as the fourth side in the tournament, which will also feature the Netherlands, Cameroon, and the Ivory Coast, at the Hong Kong Stadium from July 30 to August 2. The four teams will compete for the ING Cup, which will act as the final preparation for the Olympic tournament in Beijing. Teams have to be under-23 but three over-age players are allowed to be included in each country's squad. The Dutch are among the favourites for the Olympic crown, having won back-to-back Uefa Under-21 Championships in 2006 and 2007. Along with Drenthe and Babel, the squad includes Valencia's Hedwiges Maduro, PSV Eindhoven's Otman Bakkal, and Feyenoord's 33-year-old Roy Makaay, whose exploits for Bayern Munich made him one of Europe's most feared strikers. 'Olympic fever is truly kicking in, so we expect great crowds at the Hong Kong Stadium on both days,' said Hong Kong Football Association chairman Brian Leung Hung-tak. 'The Netherlands, Cameroon, US and the Ivory Coast will be among the strongest teams in China and feature many world-class players.' Cameroon's Indomitable Lions have a strong pedigree at the Olympics, having won gold at Sydney 2000. This year's squad includes 20-year-old Alex Song, one of Arsenal's exciting young talents and the nephew of Rigobert Song, Cameroon's most capped player. Ivory Coast's best-known player is 22-year-old Kalou, who has played for the past two seasons with Didier Drogba at Chelsea. Drogba is also his national captain at senior level. One player who could prove to be a star of the Olympics is 19-year-old American Freddy Adu, who joined Portuguese club Benfica last August. The Ghanaian-born Adu represented the US Under-17 side when only 13. The draw and ticket prices for the tournament will be announced next Wednesday.