MADRID (Reuters) - French Open champion Rafa Nadal has been forced to withdraw from next month's Australian Open due to a stomach virus that has disrupted his recovery from a knee injury, the world number four said on Friday.

"My knee is much better and the rehabilitation process has gone well as predicted by the doctors, but this virus didn't allow me to practice this past week," the Spaniard said in a statement.

"Therefore I am sorry to announce that I will not play in Doha and the Australian Open, as we had initially scheduled."

(Reporting by Iain Rogers; Editing by John Mehaffey)