The 22-year-old has ended all three days of the major at the top of the pile and enjoyed a lead of three shots going into today's play at the Minnesota course.

She registered a two-under-par round of 70 to sit nine-under for the tournament but Thailand's two-time major champion Ariya Jutanugarn is now breathing down her neck after carding 68.

Jutanugarn moved to eight-under to set up an intriguing final round tomorrow.

Americans Nelly Korda and Lizette Salas both sit on five-under and are the nearest challengers to the top two.

If Green finishes the job it will be a remarkable achievement as she has not won a title on the Ladies' PGA tour, let alone a major.

"Surprisingly, I wasn't nervous on the first tee," the Australian, who carded four birdies and two bogies in her round today, said.

"Obviously it's my first time in this position so I feel like I will be a little bit nervous come tomorrow but I think when I have more time to wait in between shots that's when I started to feel the nerves and I was like, 'okay, my heart is beating'. 

"I think I need to just slow things down and take my time and make sure I'm not rushing into any shots."

One of Green's bogeys came on the final hole which denied her a two-shot lead and could prove crucial in the final reckoning.

Jutanugarn, a former US Women's Open and British Women's Open champion, will also regret a bogey at the 16th which may have prevented her from reaching the clubhouse on level terms.

The Thai birdied six holes with two bogeys as she clawed back Green's advantage.