New York, Sep 15 (DPA) Argentine Juan Del Potro secured his tennis dream at age 20 with a 3-6, 7-6 (7-5), 4-6, 7-6 (7-5), 6-2 defeat of five-time champion Roger Federer to lift his first Grand Slam trophy at the US Open.

The sixth seed, who said he had fantasised since childhood about claiming the honours at Flushing Meadows, withstood an assault from the Swiss top seed in just over four hours Monday night to end the weather-plagued major a day late for the second year in succession.

Federer, who exploded at one point against chair umpire Jake Garner with an obscenity when he thought extra time was being given to Del Potro to challenge a line call, lost his bid to become the first man in the modern game to win six titles at the same event.

“I wasn’t allowed to challenge after two seconds. The guy takes, like, 10,” said Federer. He later added: “Don’t tell me to be quiet, OK? When I want to talk, I talk. I don’t give a … what he said.”

Del Potro, ranked sixth, is the first South American to win the New York title since compatriot Guillermo Vilas claimed the trophy on clay 32 years ago.

“This is a dream,” said the winner. “This is something I’ve always thought about. To win my favourite Grand Slam is just unbelievable.”

The victory was the first for the youngster over Federer, who came to the court with a 6-0 record in the series including half of those wins this season.

“It was tough luck today, but I thought Juan Martin played great. I thought he hung in there and gave himself chances, and in the end was the better man,” Federer said.

He noted that he “had many chances” to put the match away early.

“Six titles would have been a dream, but you can’t have them all. I’ve had an amazing summer and a great run,” Federer said.

“I’m not too disappointed, just because I thought I played another wonderful tournament. Had chances today to win, but I couldn’t take them. It was unfortunate.”

The winner will return to his career-best ranking of fifth while Federer stays number one.

The pair finished almost dead-level on winners, 57 to 56 in Del Potro’s favour, while Federer fired 13 aces to eight for his opponent. Federer had 62 unforced errors to 60 for the South American.

Federer’s frustration mounted as he couldn’t withstand the pressure from Del Potro’s forehand, and his composure fell apart in a rare display of temper.

Despite once getting within two points of a 16th Grand Slam title, Federer was unable to get over the hump.

The loss was the first for Federer at the US Open since 2003 and marked only his fifth stumble in New York against 51 wins. His record in Grand Slam finals stands 15-6.

Del Potro’s previous best showing at a Grand Slam was the semi-finals at this year’s Roland Garros, where he lost to Federer.