Australian Matt Jones remains in the lead and Jason Day is just one back midway through the third round of the US PGA Championship at Whistling Straits.

Jones is one under through his opening nine holes to move to 12-under-par for the tournament while Day, playing with Jones in the final group, is two under through the turn to be 11-under and tied second.

German Martin Kaymer, the winner at Whistling Straits in 2010 is 11-under through 17 holes, South African Branden Grace is also 11-under through 17 and American Tony Finau is 11-under through 10 to share second.

Jones opened the third round with a two-shot lead and increased it to three on the front nine only for it to close at the turn.

The Sydneysider almost holed out for eagle on the opening hole but tapped in for birdie and then added another from 10 feet on the sixth.

But a wild drive left on the ninth into a hospitality tent had Jones playing from carpet amongst the fans and although his recovery shot was within half a metre of holding the green it sat down in deep rough and a bogey ensued.

It allowed Day to bury a 12-foot birdie on the same hole to move within one.

Earlier Day matched Jones on the first with an even closer approach but then rode a rollercoaster by going bogey, birdie, bogey, birdie on his next for holes. The world No.5 steadied on the ninth to get back amongst it.

Jordan Spieth got it to nine-under through 12 holes to keep his dream of a third major this season alive.

Having already won the Masters and US Open this season, Spieth is gunning to become just the third player in history to win three of the four majors in one year, behind Ben Hogan and Tiger Woods.

Cameron Smith shot a two-under-70 to move to four under.