Hull and Vu masterfully navigated increasing winds to each end the penultimate day of the last major of the season nine under par.

Crowds followed Englishwoman Hull and roared for her first-hole birdie.

Despite a bogey immediately after, the 27-year-old stayed consistent and picked up birdies on the eighth and 11th for the third consecutive round to build momentum and a round score of 68.

Chevron Championship winner Vu put on her best showing so far as she surged up the leaderboard with three straight birdies between the fifth and seventh holes on the way to a 67-shot performance.

Third place is shared by South Korea's 2014 Evian Championship winner and Angel Yin of the US who is still in search of her first major title.

Vu's compatriot Ewing held onto her five-shot advantage for nine holes before being caught by the chasing pack.

World number 39 Ewing, who had been punching above her weight, had a torrid day as she shot a three over par total of 75.

However, she sits in sole control of fifth place just two strokes behind the leading pair going into tomorrow's decisive round.

 "I don't lose any confidence today other than I gritted my teeth when it wasn't great, and I still gave myself a chance to win this golf tournament tomorrow," Ewing said.

"Certainly, would I like to go out free-spirited and shoot another 66?

"Yes. 

"But the test was hard.

"And regardless of what the scores showed at the end of the day, I fought and gave myself a chance for tomorrow."

The Open is set to conclude tomorrow with Japan's Harula Kawasaki teeing off first at 7:55am local time.

Hull and Vu will then take to the course last at 2:20pm for the final shoot-out.