WATCH: McIlroy livid at US caddy 'crossing the line', says Donald

Rory McIlroy was made livid by Patrick Cantlay's caddy after a spat at the 18th green over behaviour which "crossed the line", team captain Luke Donald said at the Ryder Cup on Saturday.

Cantlay celebrated wildly with his USA teammates after sinking a 30-foot putt under huge pressure which eventually handed him and Wyndham Clark a win over McIlroy and Matthew Fitzpatrick and cut Europe's lead to five points overnight.

Donald says McIlroy was brushed off by Joe LaCava while the four-time Major winner was waiting to take a putt which could have halved the hole and match.

"I was there on 18. I saw it unfold when Patrick made that putt, Joe was waving his hat," Donald told reporters.

Joe LaCava like a drunk old man rambling around here

Just embarrassing #RyderCup pic.twitter.com/PkQBEh4kfB

"He (McIlroy) politely asked Joe to move aside. He was in his line of vision. He stood there and didn't move for a while and continued to wave the hat, so I think Rory was upset about that.

"It was a little off-putting because he still had to putt. And so Rory got upset, and I understand that... Rory felt like the line was crossed on the 18th green."

McIlroy was then reported to have had a blazing row with another American caddy in the carpark at the Marco Simone course in Rome, having to be pulled away and bundled into a car by Irish teammate Shane Lowry.

It’s going to be a tasty one tomorrow ??
Rory not happy with what happened on the 18th green!#RyderCup pic.twitter.com/XgpopBuNjp

"Of course they have their backs. Again, we are a big family this week. We support each other," added Donald.

The row dominated talk in the aftermath of an epic afternoon fourballs session which ended at nearly 7:00pm (1700 GMT) and gave the USA a glimmer of hope that