Top-ranked Novak Djokovic is seeded No. 1 for the U.S. Open, and five-time champion Roger Federer is No. 2, meaning they could meet only in the final.
Djokovic beat Federer for the title at Wimbledon last month. Federer reached the final after defeating Canada's Milos Raonic in the semifinal.
Federer also defeated Raonic in the semifinals of the Western & Southern Open last week.
Raonic, from Thornhill, Ont., is seeded fifth. He made it to the fourth round of the U.S. Open in each of the last two years.
The U.S. Tennis Association followed this week's ATP rankings in announcing the seedings Tuesday.
Federer moved up one spot from his No. 3 ranking because 2013 champion Rafael Nadal withdrew from the year's last Grand Slam tournament with an injured right wrist. The 33-year-old Federer is seeded at the U.S. Open for the 14th consecutive year, tied with Ivan Lendl for the longest streak, trailing only Jimmy Connors' record of 18.
Federer won the hard-court tournament every year from 2004-08, part of his record 17 Grand Slam titles.