Still stunned at her ascension to the top of women's golf, Lydia Ko says she's embracing expectations of defending her Australian Open title.

Ko enters the open, starting at Adelaide's The Grange course on Thursday, as world No 1 and reigning champion - feats she still has trouble comprehending.

"It's my third year on tour this year and it has been going much faster than I would have ever expected," Ko told reporters on Wednesday. "Obviously, it had always been my goal to be the No 1-ranked player. But I didn't imagine it to be when I was 17 or 18."

This time last year, Ko had just become the top-ranked golfer in the world - aged just 17 years and nine months.


And last September, the New Zealander became the youngest male or female golfer to win a major title since Young Tom Morris in 1868 - she won the Evian Championship aged 18 years, four months and 20 days

Ko, who turns 19 in April, has won nine other LPGA tournaments and realises she is expected to add another with consecutive Australian Open titles in Adelaide.

"Obviously, there is that pressure where everybody is looking at you, wanting you to do the best," Ko said. "But I think that almost gives you another sort of energy where you want to play some good golf and it brings the best out of you.

"I really need to embrace it - embrace the crowds that are out there ... just embrace everything around it. In some ways, you don't know what is going to happen next, but that is the beauty of the game - you can shoot 75 one day and then shoot 62 the next day - that is the cool thing about it.

"My team has really helped me to really stay more really focused on what is in front of me than think about everything else that is going on."

Ko headlines a field including Australia's top-ranked golfers Minjee Lee and Karrie Webb, and rising Canadian Brooke Henderson in a tournament carrying a $US1.3 million ($2 million) purse - the highest in this Australian summer of golf.

But Ko said the prospect of banking the US$195,000 ($297,000) winner's cheque was irrelevant.

"It would be stupid to think of it in relation to money because it gets almost a little too complicated," she said.

Instead, Ko said she was intent on taking fond memories of Australia into the open - in addition to last year's title, she won an Australian amateur title here in 2012 and collected her first professional victory at the NSW Open as a 14-year-old, also in 2012.