Play was eventually able to resume almost two hours later with McIlroy and Austria’s Bernd Wiesberger starting at 4:19pm, meaning they faced a race against time to finish before darkness descended in Louisville.

“I will hang around until next week to try to win this thing. It doesn’t bother me in the slightest,” McIlroy said.

The Open champion started with two pars before three-putting the third from long range to drop back into a tie for the lead with Wiesberger and Phil Mickelson, who had birdied the first and third.

That soon became a five-way tie when Rickie Fowler recovered from a bogey on the second with birdies at the third and fourth and Henrik Stenson picked up his third shot of the day on the fifth.

But Fowler, who finished joint fifth in the Masters and joint second in the US Open and Open this season, then moved into the outright lead by chipping in for his third birdie in succession on the fifth.

Stenson drew level again with a two-putt birdie on the seventh and when McIlroy failed to get up and down from a bunker on the sixth, the 25-year-old found himself two shots off the lead.

A superb chip from the edge of a bunker on the seventh set up McIlroy’s first birdie of the day but Fowler had also picked up a shot there and then holed from 28 feet on the 10th to reclaim the outright lead on 15 under.

McIlroy therefore found himself three off the pace but got back into contention in spectacular fashion, hitting his approach to the par-five 10th to seven feet and rolling in the putt for an eagle.

Mickelson had missed from much closer than Fowler on the 10th but made amends on the 11th to join his playing partner in the lead, the pair exchanging fist-bumps as they walked to the 12th tee.

McIlroy was looking to claim the fourth major of his career and become the first player since Padraig Harrington in 2008 to win back-to-back majors.

Lifting the Wanamaker Trophy for the second time would also see the Northern Irishman become the third youngest player after Tiger Woods and Jack Nicklaus to win four majors, just one less than the total won by the late Seve Ballesteros and two behind Nick Faldo.

It was the fourth time McIlroy had held the 54-hole lead in a major, the first leading to heartache in the 2011 Masters when he was four ahead entering the final round at Augusta only to collapse to a closing 80.

Two months later he bounced back in spectacular style to win the US Open by eight shots at Congressional before winning the 2012 US PGA by the same margin at Kiawah Island.

Last month he led from start to finish at Royal Liverpool, taking a six-shot lead into the final round before going on to win by two from Sergio Garcia and Rickie Fowler.

Fowler dropped out of the lead after a wayward tee shot led to a bogey on the 14th and when Mickelson bogeyed the 16th, McIlroy was back in the outright lead for the first time since the third hole.