Rory McIlroy, seeking his fourth major title, ended a pulsating third round of low scoring and frequent lead changes to preserve his one-shot advantage at the PGA Championship.
A stroke in front overnight heading into what is traditionally known as 'moving day', the British Open champion birdied three of the last four holes on a receptive, rain-sodden Valhalla Golf Club layout to card a four-under-par 67.
In pursuit of a third consecutive victory on the PGA Tour, McIlroy fended off a series of challenges to keep his position at the top of a tightly congested leaderboard as he posted a 13-under total of 200 in the year's fourth and final major.
Austrian Bernd Wiesberger, one of six players who held at least a share of the lead in a wildly fluctuating third round, was alone in second place after matching the day's best score with a 65.
"It's not the biggest lead I've ever had, but I'm still in control of this golftournament," said world number one McIlroy, who had been two strokes clear after seven holes before bogeying the par-three eighth.
"It's a great position to be in going into tomorrow."