Four-time Olympian Roger Federer ensured he'll collect the first singles medal of his career when he won a marathon London Olympics semi-final battle with Juan Martin del Potro.
Federer outlasted the Argentine 3-6 7-6 (7-5) 19-17 in a match that lasted four hours and 26 minutes to advance to the final against the winner between No.2 seed Novak Djokovic and No.3 seed Andy Murray.
Federer converted only two of 13 break-point chances, the second coming in the next-to-last game.
In 2008 Federer and Swiss teammate Stanislas Wawrinka won the gold in doubles. But Federer had been 0 for 3 in Olympic singles, the biggest hole in a resume that includes a record 17 Grand Slam titles.