Australian journeyman James Nitties played his last nine holes in 29 to snatch a one-stroke lead at the midway point of the Australian Open on Friday as his compatriot Adam Scott matched that 7-under 65 to surge into contention for his second national title.

Nitties shot 65 to establish a one-shot lead at 9-under par 135 over New Zealand's Ryan Fox who has had back-to-back rounds of 68.

Scott was two shots back in a tie for fourth place at 6-under, having rallied impressively after a disappointing opening 73 at Royal Sydney. He shot 30 on his back nine Friday and the 2009 winner said he must play aggressively on Saturday.

"Another day around even par and I'll probably miss the cut, so, there's no option but to play well," Scott said. "It was a good second nine holes really and I finally just got a bit of rhythm happening out there and a bit of momentum. A few putts went in and a few better shots."

American Jordan Spieth remained in strong contention after two rounds, carding a 70 to be in a tie for ninth place at 5-under.

Fox is the son of former New Zealand rugby international Grant Fox who has often been his caddie throughout his professional career. He has now teamed with South African bagman Dean Smith who caddied for An Byeong-hun when he won the PGA Championship on the European Tour last year.

"He's been on the bag for the past year and we work really well together," Fox said. "It's his first time down here and he won with An Byeong-hun around Wentworth last year so he's got some experience in the lead and I'm sure that'll help over the weekend."

Australian Rhein Gibson holds outright third place at 7-under after a 66. The 30-year-old Gibson is famous for shooting the lowest round in professional golf — a 16-under 55 — at the River Oaks Golf Club in Oklahoma in 2012.

He said he would trade that record for a win in his national open.

"A trophy, that's the missing part," he said. "Every year I've kind of gotten better and I'm in a good position heading into the weekend.

"I've put myself in the positions. Eventually I'll win one, I hope."