World number one Tiger Woods will miss this week's Arnold Palmer Invitational and says he is a doubt for next month's Masters in Augusta.

The 38-year-old American revealed external-link he has a back injury.

"It's too early to know about the Masters," said Woods. "I will continue to be evaluated and work closely with my doctors."

What now for Tiger? Iain Carter BBC golf correspondent His Masters preparations are in utter disarray now. Ordinarily he would play at Bay Hill, an event that sharpens him up competitively. Then his routine is to hit the range and work on the shots he needs at Augusta. It's a huge concern. He's 38 years of age but it's an old 38 - there is an awful lot of mileage on the clock. He has had four operations on his left knee and is someone who has punished his body throughout his career. There are an awful lot of questions about the world number one now. Read more of Iain Carter on Tiger's latest setback

The Masters is the first major of the year and begins on 10 April at the Augusta National Golf Club.

Woods, a four-time Masters champion, announced he was pulling out of the Palmer event, which begins at Bay Hill Club & Lodge in Orlando on Thursday, because he has not fully recovered from the back strain he aggravated external-link during his final round 78 in the WGC-Cadillac Championship earlier this month.

The injury also forced his withdrawal from the final round of the Honda Classic at the beginning of March.

"I personally called Arnold today to tell him that, sadly, I won't be able to play in his tournament this year," Woods said,

"Unfortunately, my back spasms and the pain haven't subsided."

Meanwhile, it has been announced that Torrey Pines Golf Course near San Diego will host the 2021 US Open.

It will be the second time Torrey Pines has hosted the tournament after Woods defeated Rocco Mediate after a play-off to win the title in 2008.