Serena Williams has turned down the offer of a wildcard to the Sydney International ahead of an expected Australian Open defence.

The 23-time grand slam champion has not played competitive tennis since triumphing in Melbourne 12 months ago when she was pregnant with her first child.

Williams, who lost an exhibition match to Jelena Ostapenko in Abu Dhabi last weekend, has not yet committed to playing, but tournament director Craig Tiley spoke of his confidence that the 36-year-old will compete.

Sydney International tournament director Lawrence Robertson has now revealed that he attempted to convince Williams to fine tune her game ahead of travelling to Melbourne, but the offer was refused.

"She's taken a decision that she wants to focus fully on her defence of the Australian Open and we've got to respect that," Robertson said in quotes reported by the Sydney Morning Herald. 

"She's got to ease herself back in. Having a child is a big thing.

"We were always hopeful but, at the same time, she's earned the right for her to choose her schedule and for her to time her own return to the sport.

"The likelihood is she'll probably go and hit some balls somewhere, most likely in Melbourne. There are a couple of exhibition events down there that she may choose to play in.

"We've got such a strong field here. Sometimes when you're easing your way back in, what you don't want to do is come on court.

"The 30th best player in the world will give Serena a good game, even when she's at the top of her game. We can understand her decision."