Tiger Woods has revealed he pulled out of the Ryder Cup because he did not feel he could have won a point for the United States.

Woods, 38, last week withdrew himself from contention for the competition, which gets under way at Gleneagles in Scotland on September 23, and has ruled himself out of any further action until December as he attempts to get to the root cause of persistent back problems.

"Physically, I couldn't do it," Woods said of his decision to inform United States captain Tom Watson he was unavailable.

"I wouldn't be ready, and not being able to be there for my team-mates, the captain, assistant captain and everyone that's involved in the event, I just wouldn't be ready and I just couldn't help the team.

"When your name is called you have to be able to go out there and get a point and I just didn't feel like I could be ready enough to get a point.

"With that being said it was time to shut it down, get stronger, get more explosive again and get back for next year."

The 14-time Major winner said he is working in the gym and does not plan to pick up a golf club for a month with nothing on his agenda until his own tournament, the World Challenge tournament at Isleworth in Orlando, Florida, in the first week of December.

"I've got to be physically fit when I come back so I'll be explosive again and stable," he said.

"Obviously this year was frustrating in that I didn't really feel that I gave myself much of a chance. I first had that pain in my back and it would go away, and then it would come back, go away, come back, until eventually it never went away...It got fixed, but I took that fall on number two at the (WGC-Bridgestone Invitational) and I hadn't done any agility training yet so my hip got misaligned and everything went into spasm again.

"We got that all calmed down again but then I had to play. Now I need to keep it calm, then strengthen it and then I'll be back. That's one of the reasons I've shut it down. I'll come back in December and be ready for next year."