Furyk and Leonard will look to give the U.S. its 23rd World Cup title when the event is contested from November 13-16.
The World Cup, the final WGC event of 2003, will take place after the Tour Championship and before the Presidents Cup, which will increase the travel time for several players.
'We understand the sensitivities that time of year and scheduling puts upon the players,' said Vice President of Championship Management for the PGA Tour Jack Warfield. 'In light of this busy schedule, we are extremely happy to have first-time major champion and U.S. Open champion Jim Furyk accept as captain of the U.S. team.'
Furyk and Leonard will compete at the World Cup and the Presidents Cup, which will be held at Fancourt Hotel and Country Club in South Africa.
The Japanese team of Shigeki Maruyama and Hidemichi Tanaka will be on hand to defend their World Cup title. Maruyama won the event last year with Toshi Izawa at Vista Vallarta Golf Club in Mexico.
Ireland will be represented by Padraig Harrington and Paul McGinley, who teamed up to win the World Cup in 1997.
Three countries have been added to the mix. Teams from France, Paraguay and Trinidad & Tobago will fill in for Zimbabwe, Canada and Fiji, whose star players Nick Price, Mike Weir and Vijay Singh will be focusing on the Presidents Cup.
The highest-ranked players representing 18 countries automatically qualify for the event.
The Nation Cup, held in September in Singapore, granted spots to Myanmar, India, China and Hong Kong.
The six remaining teams will be decided through qualifiers held in Mexico and Singapore with the final two teams coming out of a second Nation's Cup qualifier to be held from October 8-11 in Mexico.