Dustin Johnson extended his lead at the WGC-Mexico Championship following a five-under-par 66 in the penultimate round.

American star Johnson moved four strokes clear of nearest challenger Rory McIlroy heading into the final round in Mexico City on Saturday.

Johnson – a 19-time PGA Tour winner – entered the third round with a two-stroke cushion and he improved to 16 under through 54 holes.

After an eagle and a birdie on the front nine, Johnson made the turn with a double-bogey on the par-four 10th. His lead dwindled but then he fired off four birdies to end the round.

Former world number one McIlroy recovered from three bogeys on the front nine for a three-under-par 68.

Four-time major champion McIlroy finished the round with four total bogeys but found solace with seven birdies.

Patrick Reed (64), Patrick Cantlay (65), Sergio Garcia (69) and Cameron Smith (68) are seven shots off the pace and in a four-way tie for third place.

Tiger Woods – in his Mexico debut – dropped one spot to ninth on the leaderboard after carding a one-under-par 70.

The 14-time major winner tallied six birdies but a tough back nine saw a double-bogey and one of three bogeys to leave him six under and 10 shots behind Johnson.

Woods – an 18-time WGC champion – has yet to win the tournament since it moved to Mexico.

Meanwhile, Justin Thomas posted a third-round 74 to be tied for 37th at even par, Phil Mickelson (72) is three over, while Jordan Spieth is three strokes further back.