Rafael Nadal and Ana Ivanovic, both ranked world No 1, have been named top seeds for the US Open, which begins at Flushing Meadows on Monday.
It is the first time that Spaniard Nadal, who replaced Roger Federer at the top of the men's rankings on Monday, has been the top seed at a Grand Slam tournament.
Federer, who has won the Open for the past four years, is seeded second, the first time he has not been the top seed in a Grand Slam since the Australian Open of 2004.
Novak Djokovic, runner-up to Federer last year in New York, is seeded third, with David Ferrer fourth.
The French Open champion Ivanovic, chasing her first US Open title, heads the women's list for the first time, with her fellow Serb Jelena Jankovic at No 2.
Svetlana Kuznetsova of Russia is seeded three, ahead of the American Serena Williams. The Olympic champion Elena Dementieva is seeded fifth, with Russia's Dinara Safina sixth and Wimbledon champion Venus Williams at seven.