American Cameron Tringale set the early clubhouse target on day one of the US PGA Championship as Kiawah Island lived up to its fearsome billing.

The longest course in major history had dominated the build-up to the season's second major, with the Pete Dye-designed Ocean Course on South Carolina's Atlantic coast capable of playing to a maximum of 7,876 yards.

And although it was playing to 'only' 7,660 yards on Thursday, the length and windy conditions were proving a tough test for the world's best players.

Tringale covered his first 11 holes in four under par before dropping shots on the 12th and 15th and eventually signing for a two-under-par 70, with compatriot Talor Gooch and England's Paul Casey shooting 71.

Rory McIlroy, who won by eight shots when the US PGA was last staged at Kiawah in 2012, was also among the early starters and had been installed as the pre-tournament favourite following his recent victory at Quail Hollow.

However, the 32-year-old began his campaign for a first major title since 2014 by carving his drive on the 10th, his opening hole, into the water.

After taking a penalty drop McIlroy hit his third shot into a sandy waste area behind the green, but despite appearing to catch his fourth shot a little thin, got up and down to salvage an opening bogey.

Birdies on the 11th and 12th got McIlroy into red figures, but bogeys on the 16th, first and second dropped the four-time major winner down the leaderboard on two over par.

Before play had got under way at 7am local time, former Open champion Francesco Molinari had been forced to withdraw from the event with a back injury in another blow to his chances of making Europe's Ryder Cup team for September's contest at Whistling Straits.

The Italian became the first European player to compile a perfect 5-0 record in Paris in 2018, but has slipped to 144th in the world and is currently 42nd in the qualifying race.

"Unfortunately I had to withdraw this morning during my warm-up for an issue to my lower back," the 38-year-old wrote on Twitter.

"I hope to get better quickly and be able to go back playing as soon as possible. Thanks everyone for the support."