Discuss as:

Roger Federer defeats Juan Martin del Potro in longest-ever Olympic tennis match

Adrees Latif / Reuters

Switzerland's Roger Federer rests on the net after winning his men's singles tennis semi-final match against Argentina's Juan Martin del Potro (L) at the All England Lawn Tennis Club during the London 2012 Olympic Games, on Aug. 3.

Clive Brunskill / Getty Images

Roger Federer of Switzerland celebrates his 4-6, 7-6, 19-17 win over Juan Martin Del Potro of Argentina in the Semifinal of Men's Singles Tennis on Day 7 of the London 2012 Olympic Games at Wimbledon on Aug. 3, in London, England.

Martin Bernetti / AFP - Getty Images

Argentina's Juan Martin del Potro returns the ball during his men's singles semifinal round match against Switzerland's Roger Federer during the 2012 London Olympic Games at the All England Tennis Club in Wimbledon, southwest London, on Aug. 3.

Stefan Wermuth / Reuters

Switzerland's Roger Federer wipes his forehead during his men's singles tennis semi-final match against Argentina's Juan Martin del Potro at the All England Lawn Tennis Club during the London 2012 Olympic Games, on Aug. 3.

AP reports -- Roger Federer clinched the first singles medal of his career Friday in an Olympic marathon, winning 19-17 in the final set against Juan Martin del Potro.

The semifinal match lasted 4 hours, 26 minutes, and Federer rallied to win 3-6, 7-6 (5), 19-17. He converted only two of 13 break-point chances, the second coming in the next-to-last game.

With the comeback victory, four-time Olympian Federer is assured of at least a silver. On Sunday he'll play in the final against the winner of the second semifinal between No. 2-seeded Novak Djokovic of Serbia and No. 3 Andy Murray of Britain.

Continue reading on NBCOlympics.com.

Related links on PhotoBlog:

Andy Rain / EPA

Juan Martin Del Potro of Argentina reacts during his men's semi final match against Roger Federer of Switzerland during the London 2012 Olympic Games Tennis competition in Wimbledon, Greater London, Britain, on Aug. 3.

Andy Rain / EPA

Roger Federer of Switzerland at the net with Juan Martin Del Potro of Argentina whom he defeated 19-17 in the final set of their semi final match during the London 2012 Olympic Games Tennis competition in Wimbledon, Greater London, Britain, on Aug. 3.

/

Click for more from the 2012 summer games in London.