Phil Mickelson has put himself on track for a long-awaited major breakthrough at the U.S. Masters after overnight pacesetter Justin Rose and Tiger Woods both fell back in testing conditions at Augusta.

Left-handed Mickelson, who has placed third in his last three Masters starts, fired a three-under-par 69 in the third round to tie fellow American Chris DiMarco for the lead at six-under 210.

DiMarco, who caught Mickelson with a birdie-three at the 14th where he struck an eight-iron approach to within a foot of the flag, carded a 68 in bright sunshine.

Widely regarded as the best current player yet to win a major, Mickelson had a chance to snatch the outright lead at the par-four 17th.

However, his birdie putt from eight feet slid past the hole just as he started to pump his fist in celebration.

The former world number two then overshot the green with his approach at the last and had to hole a tricky seven-foot putt to save par.

Britain's Paul Casey, competing at Augusta for the first time, carded a four-under 68 to secure third place on four-under 212, with European Ryder Cup captain and twice champion Bernhard Langer a further shot back in a tie for fourth after a 69.

Level with German Langer was triple major winner Ernie Els, who returned a 71.

Chasing his long-awaited major breakthrough in his 47th start, Mickelson saved par at the first with a deft up-and-down from the left of the green before sinking a 25-foot birdie putt at the par-four third.

He then holed short birdie putts on seven and eight before missing an opportunity from eight feet at the par-four ninth to stretch his lead to two.

World number one Woods struggled in the conditions, carding a three-over 75 after hauling his way back into contention with a second-round 69.

HITTING BACK

Bidding for a third Masters title in four years, he dropped a shot at the first after finding a fairway bunker off the tee before hitting back with a birdie-four at the 575-yard second.

However, he bogeyed the par-three sixth, where he overhit the green, and another bogey followed at the par-four ninth as he slipped back to two over.

With the wind swirling through the Georgian pines on the back nine, the eight-times major champion double-bogeyed the par-five 13th and also dropped a shot at the par-four 14th before repairing some of the damage with birdies at 15 and 17.

Britain's Rose, who had preserved his two-shot cushion with a one-under-par 71 in Friday's second round, tumbled down the leaderboard with six bogeys in a front nine of 42 as Augusta's slick greens were quickened by the blazing sun.

The 23-year-old Englishman dropped further shots at 11, 13 and 15 to lie nine adrift of the lead with two holes remaining.

Earlier Sweden's Fredrik Jacobson had surged into contention with a sparkling five-under-par 67 for a 54-hole total of one-under 215.

Jacobson, who opened with successive 74s, reeled off six birdies before finishing within three strokes of the early lead.

Although the 29-year-old Swede dropped his only shot of the day at the last, he produced a near-flawless display of golf in testing conditions at a sweltering Augusta.

"The main thing was getting the putter to work today," Masters debutant Jacobson told reporters. "If I can put together another score like that tomorrow, I have a good chance.

"It would be nice if I am within four shots of the lead tonight," added the Swede, who produced top-six finishes at last year's U.S. and British Opens.