Charlie Wi holds a three-shot lead at the Pebble Beach National Pro-Am after a three-under round of 69 on a second day which saw Tiger Woods falter.

With the weather changing from sunny to drizzle through the day Woods shot a two-under 68 on the easiest of the three courses, the Monterey Peninsula Country Club, to lie at six under at halfway.

Wi took 29 putts but his up and down round included five birdies, an eagle and four bogeys.

Dustin Johnson, a winner of the tournament in 2009 and 2010, shot an even-par 72 on Spyglass Hill to sit three shots behind Wi.

Woods told the PGA Tour website: "Drove it good again today, unfortunately just didn't make enough birdies."

Lying in a tie for 16th, Woods added about the deteriorating weather: "The golf course got a little interesting coming in.

"I was hitting the ball in the wrong spots. And the greens started to get a little bumpy with the softer conditions."

Ireland's Padraig Harrington ended the day in a tie for third at eight under.

Harrington added a 66 to his first round 68 to join Americans Brian Gay and Brendon Todd, Fiji's Vijay Singh and New Zealand's Danny Lee.

England's Greg Owen added a 67 to his opening 68 to sit on seven under in a nine-way tie for eighth.

Russell Knox finished the day on three under, two shots ahead of fellow Scottish golfer Martin Laird who was joined on one under by Ian Poulter.

His fellow Englishmen Gary Christian and Brian Davis were level par.