By Joshua Schneyer

RIO DE JANEIRO (Reuters) - Argentina's Juan Martin del Potro won a semi-final thriller against Spain's Rafa Nadal on Saturday, outgunning the Spaniard 5-7 6-4 7-6(5) in a nervy final set tie-breaker to advance to the Olympic singles final.

Del Potro will face Britain's defending Olympic champion Andy Murray in the final on Sunday.

Nadal, who won singles gold at the 2008 Beijing Games and has already captured gold in Rio in the men's doubles, will face off against Japan's Kei Nishikori for a bronze medal.

(Additional reporting by Drazen Jorgic; Editing by Alison Williams)