Tiger Woods and Vijay Singh set up a showdown at the Wachovia Championship after moving into a joint lead with Aaron Oberholser at Quail Hollow in Charlotte.

They are one shot clear of Jason Bohn and Ted Purdy.

Overnight leader Padraig Harrington fell three shots off the pace after a dreadful finish.

Woods, in his first event since the Masters more than three weeks ago, was nowhere near his best, but again showed he can contend without being on top form.

Woods hit some errant shots, finding just five fairways, but used a sharp, short game to avoid dropping a stroke until his final hole, the par-four ninth, where he pulled his drive into trouble and had to pitch out almost sideways.

"I'm very pleased with my score," Woods said of his four-under-par 68, which matched the day's best score. "I missed a couple of short ones but also got away with a couple of bad drives.

"I pretty much have maximised my (two) rounds. I didn't hit it very good today. I made a couple of good par saves to keep the middle part of my round going."

He joined Singh (71) and Oberholser (69) at six-under 138, but for a while it looked like Harrington would end the day in front.

The first-round leader made a poor start, three bogeys in the first four holes, but he fought back nicely with four consecutive birdies starting at the 10th, only to throw it all away at the end.

He fell back into tie for the lead with a bogey at the tough par-three 17th but much worse followed at the par-four 18th where he made a disastrous triple bogey to shoot 75 and fall three shots behind.

After driving into the right fairway bunker, the Irishman pulled his second shot into the creek left of the green. He took a penalty and pitched his fourth shot to 15 feet, compounding his earlier mistakes by three-putting.

Singh also made a tardy start, dropping two shots in his outward half, but he came home strongly, playing his final three holes in three-under.

His highlight was an eagle at his 16th hole, the par-five seventh, where he where he hit a mighty three-iron to three feet.

"That's the way this game is," he said. "I wasn't playing bad. I just wasn't putting it together and then all of a sudden, something good happened."

Oberholser came home with birdies at his final three holes and said: "I'm striking the ball very well but I'm going to have to putt better.

"I'll be honest, I never feel totally comfortable on this course. It's a lot like Augusta, where you have to think from the green backwards, and play accordingly."

Oberholser will get to play his third round in relative peace and quiet with Purdy, while Woods and Singh slug it out in the final pairing.

Their relationship has been a little frosty ever since Singh's caddie wore a cap with the words 'Tiger Who?' stitched on the back before their singles match at the 2000 Presidents Cup.

Darren Clarke, who is desperately looking for a return to form, withdrew from the event after an opening 76 on Thursday.