The Northern Irishman was two shots adrift of overnight leader Adam Scott heading into the penultimate round, but delivered a signal of intent to his Australian rival with a birdie at the first hole of the day.

McIlroy, a four-time major winner, went on a charge with birdies at the fifth, seventh and 10th to propel himself to the top of the standings.

He then completed his round by securing pars at the remaining eight holes, which means he has failed to drop a shot during his last 33 holes and has moved onto 12-under-par.

“You have to just keep going and set yourself a target,” said McIlroy, who is playing with a new cross-handed grip.

“Basically, I can't play defensive, defensive isn't my style.

“I need to go out there and be aggressive and be assertive.”

Scott’s challenge stuttered, as the Australian had a mixed round which included two birdies but three bogeys.

It saw him drop back to nine-under-par ahead of the final round, level with the defending champion Dustin Johnson, after the American shot a one-under round of 71.

Fellow Americans Phil Mickelson and Bubba Watson are a further shot back, but their hopes of victory could depend on producing a stunning final round.

The winner of the Championship is set to be presented with the trophy by Donald Trump, despite the businessman currently leading the race for the Republican nomination to become President of the United States.