Rory McIlroy recovered from a slow start to boost his chances of a second Major title in succession in the weather-affected US PGA Championship.
McIlroy briefly dropped three shots off the lead when he bogeyed the par four 12th, his third hole of the day, but bounced back with a birdie on the next and made another from 18 feet on the 15th as more rain fell at Valhalla.
And when the 25 year old Open Champion holed from 30 feet for an eagle on the par five 18th, he suddenly held a two shot lead over US Ryder Cup vice-captain Steve Stricker and fellow American Ryan Palmer.
England's Lee Westwood and American Kevin Chappell were also six under and among the later starters yet to begin their rounds.
McIlroy had not looked in top form in the early stages of his round, pushing his opening drive into the crowd on the par five tenth and failing to convert a birdie putt from ten feet, although a par was at least two shots better than he managed there on Thursday after hooking his second shot out of bounds.
Another birdie chance went begging on the 11th and the World Number One then bogeyed the 12th, pulling his drive into the gallery and failing to get up and down from a greenside bunker.
McIlroy, who followed his Open victory with a first World Golf Championships title in the Bridgestone Invitational on Sunday, got back on track with birdies at the 13th and 15th and missed from six feet for another on the 16th after a towering four iron approach from 224 yards.
But he made amends from much longer range on the 18th to reach the turn in 33 and pile the pressure on the chasing pack.
Play had got under way in torrential rain at 7:30am but was suspended just 20 minutes later with the first group of joint overnight leader Palmer, Ireland's Shane Lowry and Bob Sowards still on the first green.
Two members of the greenkeeping staff at Valhalla had been attempting to clear water from the putting surface with squeegees, but that proved an impossible task as the rain intensified.
The rain eased enough for tournament officials to announce play would restart after a delay of 45 minutes, although preferred lies could not be used as they were not in force when the round got under way.
The delay meant McIlroy's tee time was pushed back until 9:25am and by then the rain had stopped, leaving the course vulnerable to the kind of "target golf" the Northern Irishman prefers.
The conditions did not seem to favour Stricker, but the 47 year old - named on Wednesday as Tom Watson's final vice-captain for The Ryder Cup at Gleneagles - had covered the back nine in 32 to improve to six under.