Tiger Woods is in danger of missing his first Masters tournament because of injury.
The world number one admits he does not know if he will line up in the Augusta event next month due to back trouble.
Woods has not missed a Masters since making his debut as an amateur in 1995 and has won the event four times.
The 38-year-old announced on Tuesday that he would be unfit to play in the Arnold Palmer Invitational, a PGA Tour event which begins on Thursday at Bay Hill Club and Lodge in Orlando.
Woods hopes to recover for the Masters, which begins on 10 April, but could offer no reassurance he will play at the first major of the year.
Confirming on his website that he was pulling out of the Palmer event, Woods said: "I personally called Arnold today to tell him that, sadly, I won't be able to play in his tournament this year.
"I would like to express my regrets to the Orlando fans, the volunteers, the tournament staff and the sponsors for having to miss the event. Unfortunately, my back spasms and the pain haven't subsided.
"It's too early to know about the Masters, and I will continue to be evaluated and work closely with my doctors. I feel badly that I won't be able to play in this great tournament this week."
Woods suffered back spasms at The Barclays tournament last summer and the problem has persisted.
He has played just three events on the PGA Tour this year, and completed just two of those, having pulled out of the recent Honda Classic during his final round when injured.
He decided he was well enough to compete at the WGC-Cadillac Championship in Doral, Florida, days later, however he could not challenge on the final day after carding a 78.