Tiger Woods was left wondering what might have been after saving his best till last on the final day of the US PGA Championship in San Francisco.

After opening with a 68 at Harding Park, consecutive rounds of 72 left Woods out of contention for a 16th major title and among the early starters on Sunday.

But the 44-year-old put in a characteristically professional display to card five birdies and two bogeys in a closing 67 to finish one under par overall in just his fourth tournament of 2020 due to injury and the coronavirus pandemic.

Woods got off to an excellent start with birdies on the fourth, fifth and seventh before dropping a shot on the eighth after failing to get up and down from a greenside bunker.

The back nine looked to offer numerous scoring opportunities thanks to some accessible pin positions and Woods birdied the 14th and 17th before dropping a shot on the last following an errant drive.

"I drove it like I did on Friday, my irons were a little crisper and I hit better putts," Woods said. "An under-par tournament score, that's what I said I wanted yesterday and made it happen today."

Asked what he would take out of the week, Woods added: "What I get out of this week is that I felt competitive. If I had made a few more putts on Friday and Saturday I would have been right there with a chance.

"I fought hard and today was more indicative of how I could have played. (But) that's golf. We lose way more tournaments than we win. This is one of those weeks where I didn't quite make the putts when I needed to, and I missed a couple shots on the wrong sides.

"But, overall, I think I had one three-putt for the week and I had no doubles, and that's always something that you want to do going in throughout 72 holes of a major championship. Unfortunately I didn't make enough birdies and I'm not there with a chance come this afternoon."

The best rounds of the day so far had come from An Byeong-hun and Ryan Palmer, who both shot 64 in some style.

Palmer holed from 12 feet for an eagle after driving the green on the short, par-four 16th and birdied the last two holes, while An's round included a hole-in-one from 189 yards with a six iron on the 11th.

The top 17 names on the leaderboard were separated by just four shots in what promised to be a thrilling conclusion to the first major championship in 13 months.

Dustin Johnson held a one-shot lead on nine under par, with fellow Americans Cameron Champion and Scottie Scheffler his nearest challengers.

Defending champion Brooks Koepka, who is chasing an historic third straight victory in the event, was two shots off the lead alongside Collin Morikawa and England's Paul Casey.