Serena Williams has announced that she will not defend her Australian Open title in Melbourne later this month as she has yet to return to full fitness.

Serena Williams, 36,returned to action against French Open champion Jelena Ostapenko in Abu Dhabi last week, just four months after giving birth to daughter Alexis Olympia.

Williams has been in full training for just a month, though, and the 23-time Grand Slam winner has decided to delay her return to the big stage until she regains her sharpness.

“After competing in Abu Dhabi I realised that, although I am super close, I’m not where I personally want to be,” she said in a statement. “My coach and team always said ‘only go to tournaments when you are prepared to go all the way’.

“I can compete – but I don’t want to just compete, I want to do far better than that and, to do so, I will need a little more time.”

Serena Williams was eight weeks pregnant last year when she triumphed for a seventh time at Melbourne Park to claim an Open-era record 23rd Grand Slam title.

Tournament director Craig Tiley called Williams’ efforts to try and be ready for a title defence at the Australian Open “Herculean” and said she transcended the sport.

“It was never going to be good enough for her to just compete, she wants to give herself the best chance to win.

“I’ve been in constant contact with Serena and her team and know this is why she has pushed it and pushed it until the eleventh hour to make her final decision,” Tiley said.

Williams is the latest tennis star to withdraw from the year’s opening Grand Slam, which will be played from Jan. 15 to Jan. 28.