Rory McIlroy
McIlroy sits 13 under par heading into Sunday.Getty

Rory McIlroy remains on course to secure consecutive major championships after maintaining a one-stroke advantage on day three of the US PGA Championship.

The world number one was not at his scintillating best on the penultimate day of the competition as he shot a four under par 67 to keep hold of a slender lead at 13 under at Valhalla.

Bernd Wiesberger remains hot on the heels of McIlroy after he finished Saturday with three birdies to card a 65 and open up a shot lead on third placed Rickie Fowler (67).

2013 Open champion Phil Micklelson and Australian Jason Day sit joint fourth ten under par with Louis Oosthuizen (67), Henrik Stenson (67), Mikko Ilonen (69) and Ryan Palmer (69) sat in fifth, all at nine under.

In his quest to replicate Padraig Harrington's 2008 feat of taking the Open and US PGA titles in the same year, McIlroy just about did enough to maintain his lead in Kentucky. Tame chips on the eighth and 12th holes in between an over hit approach shot on the 11th provided moments of concern for the Northern Irishman, but three exquisite birdies on the final four holes ensured he would go into the final day with a lead intact.

"I would rather be the guy that's being chased and have that shot advantage than not," McIlroy told Sky Sports.

"I didn't have my best stuff for some of that round," he continued. "There were stretches of golf in that round that felt really good. I finished well but the middle of the round was pretty scrappy.

"But saying that, there was only two bogeys. I scrambled well. But yeah, the last two days, it has not been quite as good as I can be.

"If everything does click tomorrow, then obviously I feel like there's a very low score in me. I'll take sort of scrapping it around in 67 if it puts me in this position again."

"Standing on the first tee (on Sunday) is going to feel different than how it felt a month ago at Hoylake, because it is going to be a shootout.

"You know the conditions are soft. Guys are going to make birdies and you know that you're going to have to make birdies, as well to try and win."