Rory McIlroy led on his own as the third round of the US PGA Championship resumed on Kiawah Island’s Ocean Course.

Among 26 players unable to finish their third rounds because of a thunderstorm on Saturday, McIlroy began again on the tenth tee tied with Vijay Singh on six under par.

McIlroy looked like leading on his own again, but Singh saved par on the ninth with a 15 foot putt after pulling his approach into the rough.

Tiger Woods resumed with an eight foot putt for par on the eighth green - and lipped out.

His fourth bogey of the round dropped the 14-Major Champion, who was tied for the lead at halfway, to joint 17th on level par, six strokes behind playing partner Singh – who at 49 was looking to become the oldest Major Champion in history.

Woods had to work hard not to lose further ground. He drove into the sand, could not make the green, but chipped to four feet and made it for an outward 40 - eight more than McIlroy, who safely parred his first hole of the day.

McIlroy looked shocked when he missed a three foot birdie chance at the long 11th, but Singh handed him the outright lead by pulling another iron shot and this time failing to get out of the sand at the first attempt.

The Fijian's first bogey of the round left him five under, with McIlroy one ahead and both Carl Pettersson and Adam Scott four under following the Australian's bogey six at the 11th.

Graeme McDowell's hopes were hit when a double bogey on the 497 yard 13th took him down alongside Woods on level par, although he did hit straight back with a birdie two.

McIlroy's putting let him down again on the 13th, a five foot par miss this time - and it cost him top spot as Singh birdied the 11th from the same distance.

Woods also made four there and at one under was five back.

Things continued to see-saw, but suddenly McIlroy went from one behind to three clear of the field.

He holed from ten feet at the 15th and two-putted the long 16th for another birdie, whereas Singh bogeyed the 12th and 14th after missing the green both times.

He fell into a tie for second with Pettersson and also South African Trevor Immelman, while Woods made another birdie from 12 feet at the 13th and had climbed back to joint eighth on two under.

McDowell made it a hat-trick of birdies from the 14th and by getting up and down from sand on the short 17th was tied for fifth on three under.

Pettersson two-putted the 16th to cut McIlroy's lead back to two and the Northern Irishman did well to keep it that way, getting up and down from sand at the 223-yard 17th.

Singh went from bad to worse, double-bogeying the 15th, and although Woods parred the hole he had his problems there too - with a cactus after carving his drive.

The thorns stuck in his trousers and shoes and he was limping badly at first before removing what he could with the aid of a towel.

McDowell was in trouble on the last. In sand for two well short of the green, he could not find the putting surface and by failing to get up and down double-bogeyed for a 71 that left him six adrift and joint tenth.