The 30-year-old produced a stunning round of 69 to put some distance between him and the other challengers, including Tiger Woods.

The world number one dropped a shot at the final hole which may prove costly when the tournament comes to an end.

Also still in contention are Americans Rich Beem, Fred Funk and Mark Calcavecchia.

The rest of the field struggled on a day dominated by bad weather and raging winds.

As it happened on day three:

0050: Mark Calcavecchia drops a shot at the final hole, but Justin Leonard and Rich Beem both make par.

0040: Fred Funk finishes a round of 73 to huge cheers - the veteran is perhaps the most popular player at the tournament.

0035: Rich Beem drops another shot at the 17th hole.

0032: Tiger Woods finishes his round with a bogey - his only one of the entire round - he will start the final round as he did the third, at four under.

0022: Funk three-putts and drops a shot at the 17th.

0011: Mark Calcavecchia drops a shot, Justin Leonard gains a shot to stretch his lead to two at the 16th.

2356: Leonard birdies the 15th to take the outright lead for the first time during the third round - Calcavecchia birdies the hole as well.

2345: Fred Funk's incredible story continues - he birdies the 15th to move back to six under.

2341: Tiger Woods' playing partner Chris Riley birdies the 15th to move to four under.

2333: Beem drops his first shot of the day at the 14th - he is now tied for the lead with Justin Leonard.

2319: A clumsy three putt from Calcavecchia sees him drop a shot at the short 13th.

2310: Funk drops a shot at the short 13th to drop back to five under.

2307: Justin Rose shows his extreme courage by making a birdie at the 15th to get back to level par.

2304: Calcavecchia makes a birdie at the 12th to get back to six under again.

2241: Beem moves to eight under after a birdie at the 11th.

2229: Fred Funk birdies the 11th and moves back to six under.

2220: Woods grabs his first birdie to get to five under, while Leonard's birdie at the 10th gives him a share of the lead. But only ten players are still under par.

2202: Woods records his tenth consecutive par.

2201: Calcavecchia drops his first shot of the day at the ninth hole.

2139: Rocco Mediate and Greg Norman birdie the 14th and both players move up the championship leaderboard.

2125: Justin Leonard birdies the seventh to get back to six under.

2115: Justin Rose drops another shot to fall to one over par.

2100: A double bogey at the sixth drops Retief Goosen back to two under.

2050: Justin Leonard misses a five foot putt at the fifth hole and drops his first shot of the day.

2048: A double bogey for Rose takes him back to level par for the championship.

2035: Rose hangs on to his score of two under with a great save at the seventh - Australian Peter Lonard moves to three under.

2031: Goosen drops another shot to fall to four under.

1954: Pierre Fulke drops a shot at the second and falls back to three under.

1940: Rich Beem birdies the first hole to take the outright lead on seven under.

1931: Fred Funk drops a shot after finding an unplayable lie in a fairway bunker.

1926: Justin Leonard, Mark Calcavecchia and Rich Beem start their rounds.

1914:Fred Funk, Retief Goosen and Pierre Fulke tee off.

1900: Tiger Woods tees off and finds the fairway.

1847: Padraig Harrington double bogeys the first and must be considering retiring in order to avoid further injuring his neck.

1844: New Zealand's Michael Campbell birdies his first hole to move to two under par.

1819: Ireland's Harrington has apparently pulled a neck muscle on the driving range and has to receive physiotherapy. He has already taken his tee shot at the first hole and the injury is clearly hampering his swing.

1810: Ernie Els tees off, five shots off the lead while Nick Faldo birdies his first hole to go to two over par.

1746: Vijay Singh is the first man to make a birdie in round three, taking a three on the first to go to even par.

Second round news:
1646: The final group completes the 18th to bring the second round to an end, with five players tied on six under par and Tiger Woods just two strokes back.