Tiger Woods returned to form at one of his favourite venues before a pair of dropped shots cost him a share of the lead at the weather-affected WGC-NEC Invitational on Thursday.

The world number one was five-under-par through 15 holes but lost his way late in the opening round with back-to-back bogies at the Firestone Country Club as darkness descended on the course.

Due to heavy overnight rain that continued through the morning, tee times were delayed by almost six hours, forcing the field to set off in the middle of the afternoon.

Eventually the 76 competitors started off front and back nine tees in threesomes, before play was halted again for 46 minutes due to lightning.

The players returned to the course until the round was suspended due to darkness with 60 players left to finish their opening 18 holes on Friday.

Ryder Cup-bound Stewart Cink is five-under-par through 10 holes and leads by one shot over Australian Rod Pampling at four-under-par.

Woods is three-under-par through 17 holes and is tied for third with Zach Johnson who has played 12 holes and Paraguay's Carlos Franco through 11 holes.

Of those that had completed their rounds, France's Thomas Levet and U.S. Ryder Cup team members Jim Furyk and Davis Love III shot two-under-par 68s to share the clubhouse lead.

THREE BIRDIES

Woods made a poor start to his round with a bogey on the par four first hole, but quickly made up for it with three birdies in a row and eventually made the turn at two-under-par 33.

He then had a streak of three birdies over a stretch from the 12th through 15th holes to take the lead before his late lapse.

"I was both playing well and throwing away too many golf shots," Woods said. "When you make seven birdies on this golf course, that's not easy to do, and then you throw it right away with four bogeys, that's not very good."

Cink, recently picked for the Ryder Cup team by Captain Hal Sutton sought to justify his selection with an error-free five birdie performance over 11 holes.

"I was playing really well out there," Cink said.

"I hit a lot of fairways, and with these conditions, the rain really changed the course since yesterday. It's playing vulnerable.

"Lift, clean and place, no wind, soft greens. If you can make a few putts and keep it in play, you're probably going to shoot a decent score."