Two-time Australian Open champion Victoria Azarenka has pulled out of next week's ASB Classic, placing her participation in Melbourne in serious doubt.

Azarenka, who claimed the ladies' crown at the season-opening grand slam in 2012 and 2013, has not played on the WTA Tour since Wimbledon in July due to an ongoing custody battle over her son.

She had hoped to relaunch her career in Auckland but informed tournament director Karl Budge on Sunday that she was not yet ready.

Budge told stuff.co.nz: "There is obviously a fair bit going on, that's been well documented and unfortunately, the result of that is that Victoria won't be here next week.

"So that's a tough one for her, she's been training hard and is a professional tennis player, that wants to be playing tennis and it's hard on us, because we were excited about having someone of her calibre playing."

Azarenka has been handed a wildcard for the Australian Open, which starts on January 15, and last week spoke of her excitement at returning to a venue at which she has enjoyed so much success.

She said: "I'm so excited about coming back to Melbourne for the Australian Open, it's my favourite tournament.

"I've won there twice and always feel so comfortable on court and the city is great.

"It's been a tough year and being able to come back to the AO will be a really positive way to start 2018."