Argentina's Juan Martin del Potro pushed Roger Federer to the limit in the semifinals of the Olympic men's tennis singles, but fell short in an agonizing 3-6, 7-6 (7-5), 19-17 defeat Friday at The All England Club.

In what was the match of the tournament in terms of quality and duration, Del Potro rediscovered the championship form that has eluded him since suffering a serious wrist injury in early 2010, but it still wasn't enough against the 17-time Grand Slam winner.

Del Potro came out on fire and consistently won the baseline exchanges against Federer in the first set, which he won after breaking his opponent's serve in the eighth game.

The Swiss came out determined to turn the tide at the start of the second set, but Del Potro's game and nerve held up as he saved all three break points he faced to force a possible match-clinching tiebreaker.

The Argentine battled back from a mini-break down in that decider, but Federer came out on top 7-5 and the stage was set for what would turn out to be an epic conclusion to the match.

The third set featured more domination by both servers. The 6-foot-6 Del Potro served six aces in the final set and held serve for the 20th consecutive time in the match to take a 9-8 lead.

But Federer, who hit 24 aces for the match, held for 9-9 and then struck blood by breaking Del Potro for the first time in the match for a 10-9 lead, putting himself just one service hold away from a spot in the gold-medal match.

In a stunning turn of events, however, the world No. 9 responded by breaking Federer's serve at love to even the match at 10-10 and the marathon continued.

Finally, in the 35th game of the third set, Federer went up a break of serve one more time and then would not be denied in his second attempt at serving out the match.

The world No. 1 kissed the Swiss flag sewn into his shirt after securing the victory, while a disconsolate Del Potro was unable to hold back the tears before exiting center court.

"Yes, it was a match to be proud of. But losing like that hurts a lot. It's hard to talk right now," Del Potro said in the post-match press conference.

"Someone has to win these matches and today it was his turn, just as (another equally important match) we played in the (2009) U.S. Open (final) it was my turn," the Argentine said, referring to his lone Grand Slam triumph.

The match, which clocked in at four hours and 26 minutes, was the longest three-set singles match in Open Era history (since 1968), although more games were played this week in Frenchman Jo-Wilfried Tsonga's 6-3, 3-6, 25-23 second-round win over Canada's Milos Raonic.

In another marathon match Friday with medal implications, Spain's David Ferrer and Feliciano Lopez fell 6-3, 4-6, 18-16 in the men's doubles semifinals to the French team of Tsonga and Michael Llodra, who saved four match points en route to the victory.

Like Del Potro, Ferrer and Lopez still have a shot at the bronze medal.

The Spaniards will square off Saturday against another French team, Richard Gasquet and Julien Benneteau, while Del Potro will face Serbia's Novak Djokovic on Sunday.

Federer will take on Britain's Andy Murray, who topped Djokovic 7-5, 7-5 in the late semifinal, for the men's singles gold medal on Sunday.

After Del Potro's defeat in the singles, he and partner Gisela Dulko were eliminated from the mixed doubles when they lost 6-2, 7-5 to Americans Lisa Raymond and Mike Bryan in the quarterfinals. EFE