Jason Day and Marc Leishman have forced their way into a tie for the lead late in the final round of the US PGA tour event at Torrey Pines in California.

Day is four-under after 15 holes and Leishman one-under-par after 11 of their final rounds to be eight-under for the tournament, tied with American Gary Woodland (11 holes) and Korean KJ Choi who is in the clubhouse after a six-under 66.

There is a six-way tie for fifth at seven-under-par creating a log-jammed leaderboard. Both men are seeking to be the first Australian to win at the iconic California coastal course and their second career win on the US PGA tour.

Starting the day one shot back, Victorian Leishman was quickly tied for the lead after he opened with a par but overnight leader Woodland made bogey.

He then hit a lovely approach to the second and drained a five-foot birdie putt to push ahead only for Woodland to match him.

A bogey on the fourth hole dropped him back out of the lead group but a birdie on the par five sixth once again saw the 30-year-old return to the top of the leaderboard.

Day opened his assault from four off the pace with a scratchy three-putt bogey and then hit his drive off the map to the left on the second.

But rather than be discouraged the Queenslander hit a stunning approach from the rough on the wrong hole and buried the birdie.

After missing a good birdie chance on the third he drained one from 16-feet on the fourth and added another on the sixth to join the contenders.

When his 13-foot effort dropped on the 12th he was just one off the pace and a crisp wedge into the 14th yielded another birdie and a tie with the leaders.