Rafael Nadal provoked panic amongst the assembled press on Sunday when he collapsed during the post-match press conference because of severe cramping in his leg, following his third round win over David Nalbandian.

The defending champion advanced to the fourth round with a 7-6 (7-5) 6-1 7-5 win over Nalbandian in stifling heat on Arthur Ashe Stadium.

Nadal had finished speaking to Spanish reporters when he stopped talking and grabbed his right leg, grimacing in pain before slowly sliding back in his chair to stretch out.

Medical staff were called for and journalists ordered to leave the room as the Spaniard was treated on the conference room floor.

"It was just cramping in the right leg, in the front and in the back. It was very painful, that's all," said Nadal after he resumed the press conference 15 minutes later.

"I will train normally on Monday. It was just a normal cramp that could have happened anywhere, but it happened in the press room. Anywhere else, nobody would have noticed."

Nadal's next opponent is Gilles Muller of Luxembourg, who won 6-1 6-4 6-4 over Russia's Igor Kunitsyn.