I just feel that I can shoot a low score out there Phil Mickelson

The American was hurt by a triple-bogey eight at the fourth as world number three Ernie Els also slid out of contention with a 72 for nine over.

"I'm not going to go into the final round defeated," said Mickelson.

Els admitted: "I played under par from the rough but made two doubles from easy positions. It's brain-dead stuff."

Mickelson, who ran up a seven-over 77 in the second round, amassed the eight at the par-five fourth after going out of bounds.

He steadied the ship with 11 straight pars before bagging a solitary birdie on 16.

"You just can't play aggressive here," said Mickelson, who finished runner-up to the late Payne Stewart at Pinehurst in 1999.

It's brain-dead stuff - I'm not swinging badly but I probably need a break Ernie Els

"The best way to make up ground is to make three or four pars rather than try to make a birdie.

"It's a tough course to turn things around on because you just can't make birdies. The more you try, the more bogeys you're going to make.

"But I'm not going to go into the final round feeling I don't have a shot.

"I just feel that I can shoot a low score out there even though I'll have to make 30-or 40-footers to do it."

"I understand realistically that might be the case. But Johnny Miller shot 63 (to win in 1973) at Oakmont."

South Africa's Els, who won the US Open in 1994 and 1997, went through the front nine in a one-under-par 34.

But he double-bogeyed the 10th and 13th holes to spoil his promising start.

He did, however, steady himself to par four of the last five holes and birdie the 190-yard 17th.

"I'm not swinging badly but I probably need a break," he added.