Argentina's Juan Martin del Potro ended Roger Federer's five-year unbeaten reign at the US Open in five dramatic sets to win his first Grand Slam title. The 20-year-old sixth seed twice fought back from a set down to win 3-6 7-6 (7-5) 4-6 7-6 (7-4) 6-2. Del Potro is the first man other than Rafael Nadal to beat Federer in the final of a Grand Slam tournament. Federer, 28, had been going for a record-equalling sixth consecutive title at Flushing Meadows. The Swiss went into the match on a 40-match unbeaten run in New York and looking to match American Bill Tilden's achievement of 1925 in winning a sixth straight championship. Another Argentine, David Nalbandian, was the last man to beat Federer at the US Open in the fourth round of 2003. He held a 6-0 career record against Del Potro, and in terms of experience there was no comparison - Federer playing in his 22nd Grand Slam final and going for a 16th major win, while Del Potro was in a Grand Slam final for the first time. However, Del Potro has rocketed up the rankings over the last year and pushed Federer desperately close over five sets in the French Open semi-finals in June. And his 6-2 6-2 6-2 demolition of Nadal in New York on Sunday left no-one in any doubt that he was a Grand Slam contender; the question was whether he could make that leap on Arthur Ashe Stadium in a final that Federer has dominated since 2004. The signs were not good early on as Federer converted his fifth break point of a lengthy second game with a beautiful forehand pass and went on to serve out the set. Del Potro then double-faulted twice in succession at the start of the second set to hand over another break, and the 23,000 spectators groaned as one as it appeared the younger man was crumbling under the pressure. It was not until the fourth game of the second set that Del Potro finally made some impression, but Federer saved three break points and soon looked poised for a two-set lead when serving at 5-4. The match turned at 30-30 when Del Potro hit a magnificent forehand down the line that was called 'out' but overturned by Hawkeye. A furious Federer protested to the umpire but there was to be no overruling the computer, and Del Potro then cracked another forehand winner to break back. From 3-3 in the tie-break, Federer mishit a forehand return before Del Potro came up with two blistering winners and converted his third set point with another. The sixth seed was now hitting the ball as he had done in his semi-final against Nadal, the power and depth constantly troubling Federer, but after breaking in game seven he allowed Federer straight back to 4-4 by dropping his own serve. Federer served his way out of trouble in game nine, despite an angry exchange with the umpire over how long Del Potro was taking to challenge with Hawkeye. Del Potro then appeared to hand the match over from 30-30 in game 10 as two double-faults in a row gave the world number one a two-sets-to-one lead. Del Potro's fitness and ability to last five sets at the highest level had remained about the only question mark hanging over his game going into the final, and he was about to dismiss it for good. Staring down the barrel at 15-40 early in the fourth set he found two huge forehand winners to save, then broke to love for a 3-2 lead, only to see Federer level at 4-4 with some brave attacking play. Federer was just two points away from the title in game 10 before Del Potro came storming back and earned break points in game 11, but a pulsating encounter would require another tie-break. There was more bad feeling over the use of Hawkeye but it was two missed forehands from Federer that allowed Del Potro to take the match into a fifth set. It was the first time since Andre Agassi beat Todd Martin 10 years ago that the US Open final had gone to a decider, and the experience and fitness of Federer suggested he would start favourite. However, the Swiss paid the price for playing to Del Potro's fearsome forehand too often and the Argentine broke for 2-0 with yet another huge winner. Federer had one chance in the next game to get back on serve but put a backhand long, and from there Del Potro played nervelessly to reach two championship points on the Federer serve in game eight, converting the second when Federer went long with a backhand. "I had two dreams this week," said Del Potro, who becomes the second Argentine to win the US title after Guillermo Vilas, who was in the stadium to witness his young compatriot's victory. "One was to win the US Open and the other one is to be like Roger. One is done, but I need to improve a lot to be like you," he said, looking at the five-time champion. "You fought until the final point. You are a great champion. I'm very happy to be here with this crown, with these people, on this court. This will be in my mind forever." After a final that lasted four hours and six minutes, Federer said: "I would like to congratulate Juan Martin on an unbelievable tournament. I had a great one but he was the best. "I would have never believed I could win five in a row here. It has been an amazing run for me." Source: BBC