"He made a joke and it was a misunderstanding," the third-seeded Serbian told reporters after he had cooled off following an angry courtside outburst that brought boos from the Arthur Ashe Stadium crowd.

"Maybe I exaggerated and reacted bad in that moment. I apologise if I reacted like that. This was just impulsive."

Roddick had commented to the crowd courtside after his previous match on the assorted maladies cited by Djokovic, who complained about stomach, hip, ankle and breathing problems during his five-set win against Spain's Tommy Robredo.

"That's not nice anyhow to say in front of this crowd that I have 16 injuries and I am faking it," Djokovic said on court after a 6-2 6-3 3-6 7-6 victory set up a semi-final clash against four-times champion Roger Federer.

Roddick, who had joked to reporters that anthrax, bird flu and SARS could be future complaints from the Serb, also tried to defuse the issue in his post-match news conference.

"It was completely meant in jest," the 2003 Open winner said. "I'm sorry he took it that way. There's nothing else to say. I don't think I was over the line. It wasn't my intention and I'm sorry he felt that way.

"Maybe I did him a favour tonight," Roddick added ruefully, suggesting he might have inadvertently fired up the Serb.

NO SIGNS

Djokovic would not detail his current physical condition but gave no signs of duress in dispatching Roddick.

"I had a very, very tough day yesterday," said the 21-year-old Serb, who was given medical treatments during the Robredo match. "Physically I was feeling very exhausted and very empty. I wasn't able to practise."

Other players in the past, including Roger Federer during a Davis Cup rubber, have accused Djokovic of stretching the rules that allow players to receive multiple medical breaks provided it was a new problem that needed to be treated by the trainer.

"Maybe people think that I'm exaggerating with these things," Djokovic said, "but I just want to make sure that everything is all right. That's all.

"It doesn't mean that if I'm inviting a doctor to the court or a physiotherapist that I'm dying."

Roddick suggested another underlying current to disquiet in the locker room with Djokovic having last year entertained fans at the National Tennis Center with on-court parodies of tennis luminaries including Rafael Nadal and Maria Sharapova.