World Number 11 Jason Dufner set the early pace in the third round of the Commercial Bank Qatar Masters with a five-under-par- 67 as he moved to eight-under overall.
World Number Five Louis Oosthuizen soon joined Dufner after a bogey-free 68, the South African's lowest round of the week.
Dufner, the third-highest ranked player in the field, started the tournament with steady rounds of 71 and 70, but fired out of the blocks on Friday morning with four birdies on the front nine.
The 35-year-old American, who won his first and second titles on the US PGA Tour last year, began the back nine with back-to-back birdies, and a bogey on the par-three 13th was the only blot on his scorecard.
"I hit the ball fairly well today and made some putts, so I'm in a good spot. Hopefully the leaders won't run away too far and I can stay within a four or five-shot range, so if I can put in a low score tomorrow, maybe they can feel a bit of the heat. I'm just going to try to do the same as I've been doing tee to green, then hole some putts," said Dufner, one of the USA's top performers in September's Ryder Cup.
"I feel good about my game. I've really hit it well. I hit it pretty well last week, but this week I've stepped it up a little bit and haven't been in much trouble off the tees."