Roger Federer pulls out of Qatar semi-final

Roger Federer has been forced to withdraw from the Qatar Open due to a back injury.

The defending champion announced that he was dropping out of the tournament 30 minutes before his semi-final showdown with Jo-Wilfried Tsonga.

"I hurt my back in the second-round match [yesterday]," said Federer. "I don't think it's the right time to risk anything right now. For Australia, I'm optimistic. It's not good, but it isn't crazy bad.

"Without playing and the right treatment I will get through it in the next few days. I have a long journey in front of me, but hopefully mid next week I should be 100% again."

Tsonga will play Rafael Nadal or Gael Monfils in the final in Doha.