'Make me look like the coward' - Sonny Bill Williams given boxing ultimatum

Paul Gallen has slapped a six-month deadline on Sonny Bill Williams to step into the ring for a heavyweight boxing blockbuster which the NRL great fears will never happen.

Turning 41 next year, Gallen accused Williams of waiting until he is all washed up before wanting to square off.

The grudge match has been slated to occur for more than seven years, since before Gallen even took up boxing 13 professional fights ago.

"The reason this all started was to fight Sonny Bill," Gallen said. "I can tell you now - and I've said this privately to a lot of people over the last couple of years and now I'm telling you publicly - it will come to a point in 12 months or two years time when he'll say, 'Let's fight'.

"I'm telling you now, it won't happen. I'm going to be past it pretty soon and that's what disappoints me.

"I've told Sonny to his face myself, I said: 'I've signed with No Limit, but I can fight you at any time.'

"That's exempt from the contract, I told him that. But I won't fight for too much longer so, unless it happens early next year, it probably won't happen.

"His reply was, 'Come on bro, you know you only need eight weeks.'

"I think he will say it in a year or two or when I'm done, to make me look like the coward, so to speak."

Asked if SBW was waiting until Gallen was past it, the former NSW State of Origin series-winning captain and premiership skipper turned pugilist said: "I think he is. That's what he is waiting for".

"Whether it's him or his manager or the people around him, I don't know. Unless it happens early next year, it won't happen.

"You have to remember, he's 36. At 36 years old, I was the Dally M lock of the year. I couldn't play NRL now, no chance in the world.

"At 32 to 36, I don't see much of a difference. Between 28 and 32, there's not much of a difference.

"You're talking 36 to 40; then next year you're talking 37 to 41 and then 38 to 42 - there's a big, big difference in those four years when you get a bit older."

Despite challenging the dual international and one-time New Zealand heavyweight boxing champion - who is undefeated in eight fights - to put up or shut up, Gallen said he could live without ever facing Williams.

"I've done so much more than I expected when I started my professional career as a footy player and boxer," he said.

"I don't really mind, I'm not going to retire and think 'I wish that that would have happened.'

"It's just something everyone wants to see.

"Every hospital visit I go to, every school I go to, everyone says 'When are you fighting Sonny Bill?' Every time.

"They don't care about anything else I've done, it's only about Sonny Bill."