The United States duo of Lisa Raymond and Mike Bryan have reached the mixed doubles Olympic semi-finals by beating the Argentinian pair of Gisela Dulko and Juan Martin del Potro.
Del Potro went into the match on the back of his marathon encounter with Roger Federer, just an hour or so before.
After an even five games to open the match, the Americans clinched the first break to lead 4-2 before also claiming the next two games to take the set 6-2.
The second set was much tighter, with neither pairing offering a single break point up until the 12th and final game before a tie-break.
Dulko and Del Potro missed their chance to close out the game and 40-30 before presenting the Americans with a match point, which they took.
The third seeds will face either top seeds Victoria Azarenka and Max Mirnyi of Belarus or the Indian duo of Sania Mirza and Leander Paes in the last four.
