Jason Day grabs lead as lightning forces suspension at Whistling Straits

When the siren sounded at 6.28 pm ET (23:28 BST) to halt the action, Day and fellow Australian Matt Jones were both out on the course and leading the tournament at nine under par.

Less than half an hour later as strong winds and heavy rain swept across the course, officials said play had been called off for the day and that the year's fourth and final major would resume at 7 a.m. local time (1300 BST) on Saturday.

World number five Day, still seeking a first major title after several close calls, had completed 14 holes and Jones 12.

English world number six Justin Rose, the 2013 U.S. Open champion, was a further stroke back with just one hole remaining while overnight leader Dustin Johnson - like Day, a serial contender in Majors who is yet to land one of golf's biggest prizes - had slipped back to -5.

Jordan Spieth shot a fine 67 to roar into contention at -6 as he seeks his third Major of the year, and Rory McIlroy is also just about in the picture after a second successive round of 71 to sit at -2 going into the weekend.

Swede David Lingmerth holds the clubhouse lead at seven under after carding a two-under 70, while Japan's Hiroshi Iwata joined the elite band of players to shoot 63 in a Major, bouncing back from his opening 77 to get in at -4.