By Mark Lamport-Stokes
LOUISVILLE Kentucky (Reuters) - The PGA Championship was heading for a gripping finish as Americans Rickie Fowler and Phil Mickelson and Swede Henrik Stenson held a share of the lead midway through the final round on Sunday.
With birdies abundant on a rain-softened Valhalla Golf Club layout receptive to approach shots, Mickelson, Fowler and Stenson took advantage of a stumbling start by overnight leader Rory McIlroy, the pre-tournament favourite.
Young gun Fowler, a top-five finisher at each of the year's previous three majors, twice held the outright lead on the front nine before being caught each time by his rivals as he reached the turn in three-under 32, 14 under overall.
Stenson, seeking to become the first Swedish male to win a major, was in even better form early on, five birdies in the first 11 holes vaulting him into a share of the lead.
Fan favourite Mickelson, hunting a sixth major title, piled up four birdies on the outward nine to get to 14 under, sinking a curling 10-footer on the ninth green that was met with huge roars from the crowd packed around the green.
With that trio leading the way in the year's final major, British Open champion McIlroy and Finland's Mikko Ilonen were a further two strokes back in a tie for fourth, at 12 under.
McIlroy rebounded from two early bogeys with a birdie at the seventh to reach the turn in one-over 36 while Ilonen was three under for the day after 11 holes.
However, the late starters faced a race against darkness in their bid to finish the 96th PGA Championship on Sunday.
Play was halted just before noon local time as heavy rain swept across the par-71 layout at Valhalla, leaving rivers of water on several fairways and pools covering many greens.
Roughly an inch of rain had saturated the course by the time play resumed at 2:44 p.m. (1844 GMT) and further thunderstorms have been forecast for later in the day, setting up the chance of a Monday finish.
A stroke in front of the chasing pack overnight, McIlroy was caught at the top when he three-putted to bogey the par-three third.
That dropped him to 12 under, level with Mickelson and Austrian Bernd Wiesberger, and moments later it became a five-way tie for the lead when Fowler birdied the fourth and Stenson the fifth.
Fowler briefly seized the outright lead in spectacular style with a chip-in for birdie from just off the right edge of the green at the par-four fifth, but was caught soon after by Mickelson and Stenson.
An up-and-down for birdie at the par-five seventh put Fowler one ahead but it did not last too long before Stenson joined him, draining a 27-footer at the par-four ninth to reach the turn in five-under 30.
McIlroy, who had bogeyed the sixth after finding a bunker with his approach, picked up first shot of the day at the seventh, hitting a delicate chip from beside a bunker to four feet and sinking the putt.
(Reporting by Mark Lamport-Stokes; Editing by Gene Cherry)