Andrea Petkovic pulls out of Olympics

German world number 18 Andrea Petkovic has been forced to withdraw from the London Olympics due to a persistent ankle injury.

The problem has kept the 24-year-old out of this year's French Open and Wimbledon.

"Really sorry to announce that I will not be competing at the Olympic Games," she tweeted. "I'm heartbroken and sad as can be but I'm just not ready yet."

No decision has yet been made on who will replace Petkovic in the 64-strong main women's draw.