All top 100 men in the rankings received direct entry Wednesday into the hard-court tournament, played Aug. 31 to Sept. 13 in New York.
Federer will be trying to become the first man since Bill Tilden in the 1920s to win the American Grand Slam tournament six consecutive times. By winning the French Open and Wimbledon this year, Federer raised his career total to 15 major titles, breaking Pete Sampras' record of 14.
Nadal missed Wimbledon with sore knees and hasn't played since late May, when he was upset in the fourth round at the French Open as the four-time defending champion. He will be trying to complete a career Grand Slam at Flushing Meadows.
Roddick won the 2003 U.S. Open. He hasn't played since injuring his right hip flexor while losing to Federer on July 5 in the Wimbledon final, which ended 16-14 in the fifth set.
Other past U.S. Open champions on the entry list are Marat Safin and Lleyton Hewitt, while Novak Djokovic, Juan Carlos Ferrero and Carlos Moya also have won major titles.
In addition to the total of 104 men who received direct entry into the field based on Monday's rankings, eight will get wild cards and 16 will earn berths in Aug. 25-28 qualifying.
The women's field is to be announced Thursday.
The winners of the U.S. Open men's and women's singles title will each receive a record $1.6 million.
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