Australian Open winner Jordan Spieth continued his relentless charge at Tiger Woods’ invitational tournament in Florida, while the host battled through nausea and vomiting in a dramatic third round.

Spieth, fresh from his victory in Sydney last weekend, fired a bogey-free nine-under-par round at Isleworth to reach 20 under, extending his overnight lead to seven shots.

Fellow American Keegan Bradley and Swede Henrik Stensen were closest to Spieth at 13 under while Woods shot a three-under round but remained last in the 18-player event he hosts to raise money for his charity foundation.

Spieth was practically flawless on Saturday, opening with three straight birdies and capping his round with a 50-foot birdie putt to take total command of the tournament.

“Felt strong coming off last week,” he said.

“Job is not done this week, but I’m a believer in my own momentum.

“I’m going to go out tomorrow with a very similar strategy to today.

“If the putts go and the breaks go my way, hopefully shoot a round like today.

“If not, I’m still going to have to shoot under par to win this golf tournament.”

The 21-year-old said he had never been 20 under on any course through 54 holes, and he had never finished a tournament that many under par.

That gave him a target for Sunday when he goes after his second straight victory.

The tournament is Woods’ first competitive hit-out after a four-month layoff due to a back injury.

“It wasn’t easy … I fought hard,” Woods said.

Woods, who had not played competitively since the PGA Championship in August because of a back injury, vomited from the first hole onward, making six birdies and three bogeys on the day.

“I’ve been throwing up for hours,” Woods said, noting he has unable to keep down food or sleep well but was not in pain and never considered quitting.

“I wasn’t doing too good at the beginning but I thought I could hang in there,” Woods said.

“The fever just broke. As the round went on I was starting to feel better.”

Woods will enter the final round 20 strokes off the lead.

Australian Jason Day, who hasn’t played since September due to a back injury, is sixth and at eight under after a third-round 70.