Former world number one Jordan Spieth has been disqualified for the first time in 263 US PGA Tour starts after signing for the wrong score at a tournament in California.

Spieth was within three shots of the lead at the turn in the second round at the Riviera Country Club in Pacific Palisades until he dropped three shots as Patrick Cantlay — playing in his group — began to pull away.

Three-time major winner Spieth made bogey on the 18th hole for a 73, leaving him 10 shots behind fellow American Cantlay, who is atop the leaderboard on 13-under-par.

But Spieth signed for a 3 on the par-3 fourth hole when he made a bogey, leading to the disqualification.

Spieth had missed the green to the left, chipped to about four feet and lipped out.

“Today, I signed for an incorrect scorecard and stepped out of the scoring area, after thinking I went through all procedures to make sure it was correct,” Spieth wrote on X.

“Rules are rules, and I take full responsibility.”

Australia’s Jason Day is tied for second place alongside American Luke List on 8-under.

Day shot a 2-under 69 in the second round.

“Overall, I’m obviously very pleased with where I’m at,” Day said.

“But I know that I could be a lot better, considering where I was after 10 (10th hole) and three-putting 11 and then bogeying 12 and 13.”

Tiger Woods made an early exit, withdrawing after six holes as he was suffering from flu symptoms.

AAP/AP