Tiger Woods' Kiwi caddie says if he had known about his famous boss's affairs he would have "blown the whistle".

But despite expressing his disappointment that the golfer let his wife and children down, Steve Williams says he is still a close friend of Woods and will stand by him.

In December, Woods announced he would take indefinite leave from professional golf to focus on his marriage to Norwegian model Elin Nordegren after he admitted infidelity. At least a dozen women claiming to be his mistresses had come forward.

In an interview with 60 Minutes last night on TV3, Williams said the past few months had been the most difficult in his life because of the feeling that the public were convinced he had known about the infidelity.

"In some people's perception, I'm involved in it and I've committed a crime or I've done wrong," Williams said.

"I've said it before. I knew nothing, and that's my answer.

"If the shoe was on somebody else's [foot], I would say the same thing: that it would be very difficult for the caddie not to know but I'm a hundred per cent telling you I knew nothing and that's that.

"I'm a straight-up sort of person. If I'd have known something was going on, the whistle would have been blown. He knows that, that's just the way I operate."

Williams said he was disappointed with Woods, who was his best man when he married Kirsty in 2006.

"Of course I'm mad at him. Why would you not be?

"I'm more disappointed that he's let his family down and let himself down.

"I'm close with his wife and he's got two lovely children and he's let them down. But I'm not mad at him towards me."

Williams said he hadn't yet spoken with Woods about the affairs.

"It's not up to me to beat him with a stick right now. He's getting enough grilling from everybody else; the media have had a feeding frenzy. I'm a friend right now. There's a time and place for everything. Obviously at some point in time, I'll have a conversation with him.

"I'd like to see him back playing on the PGA tour. That's my role right now.

"I stand by Tiger as a friend. When I talk to him, I don't talk to him about what's happened, I talk to him about the future and what we're going to try and accomplish and how we're going to get over it.

"I think life is a case of, 'You're going to try and advance from your mistakes and be a better person', so let's hope we can do that."

When asked if he thought Woods could bounce back, Williams said: "I think he will. Tiger's biggest strength is his mental strength and he's going to need all his mental strength to get over this."

Kirsty Williams, the caddie's wife, said it was hard seeing "good friends" Woods and Ms Nordegren going through the events of the past few months.

It had been tough seeing her husband having to deal with the public speculation that he knew about the affairs.

"But being so close - the four of us are so close - being so close, he couldn't know and not say something to Elin or to myself. He's just seen as a bad guy ... People are calling for him to be fired. It's not fair."