Heavy rain forced play to be suspended in the final round of the US PGA Championship on Sunday, raising the prospect of a Monday finish at Valhalla.

With the course already saturated, a torrential downpour saw play suspended at 12:53pm local time, more than two hours before the final pair of Rory McIlroy and Bernd Wiesberger were due to tee off.

Any significant loss of time would make it difficult to complete play before darkness.

Open champion McIlroy held a one-shot lead over Wiesberger as he looked to win his second major in four weeks - the fourth of his career - and a third win in succession.

Large parts of the course were quickly under water, prompting tournament officials to announce that the suspension of play would last at least an hour.

And with the rain having been forecast, it raised questions as to why tee times had not been brought forward or play started from two tees.

The Open Championship employed a two-tee start for the first time in its history last month due to the significant risk of thunderstorms at Royal Liverpool during Saturday's third round.

Play got under way at 9am from both the first and 10th tee, with the field split into groups of three rather than two.

It looked to have been an unnecessary precaution when there was no disruption to play and heavy rain which made life difficult for the early starters had stopped as the leaders went out at 11am.

But the rain returned as McIlroy gave his post-round press conference, making it difficult to hear what the 25-year-old said and leaving standing water on some of the greens.

Asked if that vindicated the decision, McIlroy laughed and pointed to the media centre roof before adding: "Definitely. I think it's the second best decision the R&A made this year, the first being bringing the Open back to Portrush."

Speaking to Sky Sports on Sunday, McIlroy said: "There's not much you can do about this weather, you just have to wait it out and hopefully we will get the chance to get out there and play.

"This course has taken a soaking this week and it has been another big downpour. Hopefully it will dry out quickly and we get to play some golf today."

Officials announced play would resume at 2:40pm, a delay of just under two hours, with nine minutes between start times rather than 10.

That meant the final group were scheduled to tee off at 4:19pm, giving them a chance to complete all 18 holes on Sunday.