Tiger Woods remains optimistic about his future despite ruling himself out of next month's US Open in order to continue his rehabilitation from back surgery.

The 38-year-old world number three last week gave the strongest indication yet that he would not be able to compete at Pinehurst from June 12-15, admitting his recovery from his March 31 operation was ''slow and tedious'' and saying he was still unable to hit full shots.

Woods on Wednesday said on www.tigerwoods.com: "Unfortunately, I won't be there because I'm not yet physically able to play competitive golf.

"I'd like to convey my regrets to the USGA leadership, the volunteers and the fans that I won't be at Pinehurst."

Woods, who underwent microdiscectomy surgery for a pinched nerve in his back eight weeks ago, has not competed since the final round of the WGC-Cadillac Championship on March 9.

He remains philosophical, though, adding: "The US Open is very important to me, and I know it's going to be a great week. Despite missing the first two majors, and several other important tournaments, I remain very optimistic about this year and my future."

This marks the sixth major the player will have missed since winning his 14th in 2008 at the US Open. Knee surgery following that victory led to an eight-month lay-off and caused him to miss the Open and PGA championships.

In 2011 he sat out the US Open and Open Championship due to knee and Achilles injuries, while this year's back surgery meant he missed the Masters for the first time in his career.

That cast further doubt on his ability to surpass Jack Nicklaus' record of 18 major titles, but Woods was bullish about his prospects.

Speaking on May 19, he said: ''The only doubts I had were prior to the surgery. I couldn't function any more.

"I've had knee surgeries in the past and, yeah, I was hurting going into it, but I was functioning. Right before this surgery I couldn't do much. Forget about playing golf at the highest level - I couldn't get out of bed.

''I was certainly doubtful at that point. Am I going to be pain-free? Am I actually going to be able to do this again where I can get out of bed and play with my kids and play golf?

''But after I had the procedure it was immediate relief and just a matter of getting through that pain part. But it wasn't the shocking or debilitating pain - it was just pain from the surgery, the incision."