MELBOURNE (REUTERS) - Jo-Wilfried Tsonga strayed on to dangerous ground when he suggested jokingly that women tennis players were "emotionally unstable" compared to the men after losing his Australian Open quarter-final on Wednesday.

The Frenchman's defeat to Swiss world No. 2 Roger Federer at Melbourne Park meant the top four men's seeds reached the semi-finals at a Grand Slam for the 15th time in the professional era.

While the seventh seed was clear in his mind why the top men dominated, he quickly realised he was on shakier ground when asked why the same was not the case in the women's game.

"You know, the girls, they are more unstable emotionally than us. I'm sure everybody will say it's true - even the girls," he told a news conference to laughter, before adding when women journalists disagreed: "No? You don't think?

"It's just about hormones and all this stuff," he added, a big smile on his face. "We don't have all these bad things, so we are physically in a good shape every time, and you are not. That's it."