SAN DIEGO (Reuters) - U.S. Open fans are set for a mouth-watering duel between Tiger Woods and Phil Mickelson over the next four days at Torrey Pines where the biggest talking point has been the state of Woods's left knee.

The American world number one has not walked 18 holes since having surgery two months ago but remains heavy favourite to win his 14th major title on a course he has played countless times since his youth.

California-born Woods has clinched the PGA Tour's Buick Invitational staged here for the last four years, and a record six times overall.

Although the set-up of the South Course is a little different with the U.S. Open featuring its traditional tight fairways, graduated rough and slick greens, Woods's comfort factor will still apply.

"I've always felt comfortable coming down here and playing, ever since my junior golf days, even though the golf course has been redesigned," the twice U.S. Open champion said, referring to changes made to the South Course in 2001.

"After the redesign, I picked up on the greens pretty quickly and I've had success ever since then."

Asked earlier this week about the condition of his knee, the 32-year-old replied: "I'm good to go. I plan on playing competitive. Come game time on Thursday, I'll be ready.

"Is it fully recovered? Probably not. It's a little sore, but not anything that I haven't dealt with before. It's feeling better.

"I feel very good about coming in and playing," added Woods, who had arthroscopic surgery on his knee two days after finishing second at the Masters in mid-April.

"It's just a matter of getting out there and playing, getting into the flow of the round and the competitive atmosphere and obviously playing well at the same time."

HIGH-PROFILE GROUPING

Woods is scheduled to tee off at 0806 local (4:06 p.m. British time) in Thursday's opening round in a high-profile grouping with world number two Mickelson and third-ranked Adam Scott of Australia.

Mickelson, likes Woods, has been a regular visitor to Torrey Pines since his junior days and, as a resident of nearby Rancho Santa Fe, will attract huge support.

A winner of three major titles, he is especially hungry to clinch his first U.S. Open after finishing runner-up on four occasions.

"Winning this tournament would be something that would help define my career," Mickelson said. "This is a once-in-a-lifetime opportunity for me to compete in the U.S. Open on the course I grew up on in the prime of my career."

Mickelson has been runner-up four times at the U.S. Open, his most painful experience coming at Winged Foot in 2006 when he squandered a two-stroke lead with three holes to play before finishing a shot behind Geoff Ogilvy of Australia.

"I've come close to winning this championship and this is a tournament I know and believe I can win," he said. "I think this golf course gives me the best opportunity to do that."

As ever at a U.S. Open, the ability to grind out pars and to stay patient when the going gets tough will be defining traits in the make-up of this week's champion.

Woods and Mickelson do not hold a monopoly in those departments, however, and no American has won the title since 2003 with South African Retief Goosen, New Zealander Michael Campbell, Australian Geoff Ogilvy and Argentina's Angel Cabrera the last four champions.

"There's a lot of other guys in the field that have a great opportunity to win this golf tournament," said Jim Furyk, who clinched his only major title at the 2003 U.S. Open at Olympia Fields in 2003.

"The focus on that elite group gives the other guys a chance to hide under the radar for our first couple of days, which is hard to do at a U.S. Open."

The 108th U.S. Open, the first to be staged on a city-owned golf course, will start at 0700 local (1400 GMT) on Thursday.

(Editing by Justin Palmer)