When competition begins Monday at the USTA Billie Jean King National Tennis Center in New York, Nadal will be trying to become the first man to win the French Open, Wimbledon and U.S. Open in the same year since Australian Rod Laver did it in 1969.
Nadal succeeded Swiss Roger Federer as the men's world No. 1-ranked player, after being ranked No. 2 for 160 consecutive weeks.
Serbian Novak Djokovic, Andy Murray of Britain, David Nalbandian of Argentina, Americans Andy Roddick and James Blake and Stanislas Warwinka are among the top 10 seeds.
Ivanovic, the French Open champion, is followed by women's No. 2 seed, fellow Serb Jelena Jankovic, Russia's Svetlana Kuznetsova, Serena Williams, Olympic gold medalist Elena Dementieva, Venus Williams, Vera Zvonareva of Russia, Poland's Agnieszka Radwanska and Russian Anna Chakvetadze.
Chakvetadze finished second last year to Justine Henin of Belgium, who retired from competitive tennis earlier this year.
Former U.S. Open champ Lindsay Davenport was seeded No. 23 and 2006 U.S. Open champ Russian Maria Sharapova will miss the 2008 tournament with a shoulder injury.