Bill Haas charged into a two-shot lead at the Farmers Insurance Open with a sparkling six-under-par 66 on the South Course at Torrey Pines in California.

Just five days after losing out in a play-off for the Bob Hope Classic, the 28-year-old American had four consecutive birdies around the turn before finishing the second round two ahead of compatriot Anthony Kim, who carded a 67 on the South layout.

Haas - bidding for a third PGA title -said: "I've put myself in that position again to have a nice 36 (holes) on the weekend which could turn this into a great week.

"So I feel good about it. I feel good about my game and I've played really well the first couple of tournaments."

Three-time champion Phil Mickelson, making his first start on the 2011 PGA Tour, was a further stroke back in a tie for third at eight under after carding a 69 on the North Course.

Also at eight under are Americans Bubba Watson (65), Rickie Fowler (71), John Daly (69), Hunter Mahan (67) and defending champion Ben Crane (66), as well as Swede Fredrik Jacobson (69).

Woods slips back

Six-times winner Tiger Woods, competing in his first event of the year, briefly closed to within two of the lead before slipping back after the turn to end the day with a second successive 69, five off the pace.

Four straight birdies early in his round had Woods three off the lead but he twice took two shots to get out of bunkers and was as many as eight shots behind until the final half-hour.

He went birdie, par, birdie for the final three holes and said: "It was a round that easily could have slipped away."

Kim played alongside Woods and birdied his opening four holes and then a tap-in birdie at the 10th saw him share the lead.

However, he bogeyed the next hole and finished with seven pars, including a three-putt on the 18th.

Kim said: "I'm really close. I know I've said it a million times. I'm not going to say it again. I've just got to make a couple of birdies and see what happens."