Gritty American Brian Harman has overcome 48km/h winds to take a three-shot lead into the final round of the PGA Tour's Texas Open.

Harman defied the guts by playing the final 13 holes without a bogey to post an even-par 72 on a day so difficult that only six players managed to break par at the TPC San Antonio.

He was at 12-under 204, three shots clear of Andrew Novak (69), with Tom Hoge (68) another shot behind.

Keith Mitchell had a 73 and was five behind. Mitchell and Novak need to win to get into the Masters next week.

It's Harman's first 54-hole lead since he won the British Open two years ago at Royal Liverpool. That also was his last victory, and he now has a great chance to end that drought.

"Just a tough day, man," Harman said. "When you get around this place and the wind blows and the pins are tucked, it's just a really hard day."

With the wind a big factor, no one could reach two of the par 5s and the average score was nearly two shots over par.

Harman was two over for his round when he made a pair of late birdies from the bunker, on the par-5 14th and the reachable par-4 17th.

Mitchell also made birdie on those holes, which spoke to the difficulty of the wind and the back nine and challenge facing everything.

Hoge might have had the most remarkable round because he didn't post a single bogey.

He was in the second group to tee off and noticed right away it was going to a challenge, not so much the crackle of the flags but the hard bounces on the green. Into the wind, or with the wind at the players' back, it wasn't easy to get anything close.

"Just tried to make as many pars as I could," Hoge said. "Even the downwind holes right off the start on hole 1, I had a 56-degree wedge, I wasn't sure I could hit the green with it because it was bouncing that much when I did land the green."

Sam Ryder, who started with a 63, had eight 5s on his card and posted a 77 to go from playing in the final group to being out of contention.

Patrick Cantlay ended the front nine with a pair of bogeys, both times missing par putts from 5 feet or closer, and shot 74 to finish eight shots behind. Jordan Spieth was in the group another shot behind after a 73.