Roger Federer will end the year as world number one for the third time in a row after clinching a hat-trick of US Open titles, the ATP announced on Monday.

The 25-year-old Swiss, who beat American Andy Roddick 6-2, 4-6, 7-5, 6-1 for his ninth career Grand Slam on Sunday, has won eight titles so far this season, compiling a formidable 70-5 record.

His Flushing Meadows victory followed his titles at the Australian Open and at Wimbledon. He also reached the final of the French Open, losing to Spain's Rafael Nadal.

Federer is only the fifth player since the ATP rankings began in 1973 to be year-end number one three successive times.