Jordan Spieth leads Tournament of Champions by five shots

Spieth will defend the US Open and Masters titles this year

Jordan Spieth tightened his grip on Hawaii's Tournament of Champions as an eight-under-par third-round 65 moved him five shots clear on 24 under.

Fellow American Brooks Koepka leads the chase after 10 birdies in a round of 63 - the best of the event so far.

First-round leader Patrick Reed is third, six shots behind Spieth.

"I have to go out and hit birdies," said Spieth as he looked forward to Sunday's final round. "I have to expect Brooks and Patrick to fire."

The world number one, who shot seven birdies and an eagle around the Plantation Course on Maui, added he would have hoped to be further ahead considering his consistent scoring.

"If I shot eight under, I would expect to be seven or eight shots clear. So for Brooks to get that score is insane," said the 22-year-old.

Irishman Padraig Harrington and Sweden's David Lingmerth are the best-placed Europeans on eleven under, with Scotland's Russell Knox climbing up the leaderboard to seven under with a four-under round of 69.

Northern Ireland's Graeme McDowell remains well off the pace, with a round of 72 leaving him two under overall.