New Zealand centre Conrad Smith is well aware of the threat that South Africa pose in Saturday's World Cup semi-final

New Zealand centre Conrad Smith has described World Cup semi-final opponents South Africa as the All Blacks' "ultimate rival."

The southern hemisphere heavyweights clash at Twickenham on Saturday, with the winners returning there seven days later for a World Cup final appointment with either Australia or Argentina.

New Zealand and South Africa last met in World Cup combat 12 years ago, when an All Blacks team containing the likes of current captain Richie McCaw, Carlos Spencer, Doug Howlett and Justin Marshall won a quarter-final clash 29-9 in Melbourne.

Since that meeting, New Zealand have beaten the Springboks 18 times from 27 starts, and their performance in demolishing France three days ago confirmed them as firm favourites to reach a second successive World Cup final.

But Smith, who has faced South Africa on 17 occasions during his 92-cap Test career, knows the All Blacks can expect a fierce examination.

"They are a special opponent, and it's a very special rivalry," he said.

"I grew up during the apartheid era, when Australia were the traditional foes, but now South Africa have come back into it and I think it's got back to where it was and they are our ultimate rival.

"There is something special about playing them, and playing them in a semi-final will be extra special.

"We have a good relationship with most teams we play, but South Africa have a special respect for the game, and that is why two minutes after the game we are able to shake hands, walk off the pitch and have a chat with them."

South Africa's trademark physical prowess surfaced during a punishing quarter-final encounter against Wales three days ago, when skipper Fourie du Preez's late try edged the Springboks home 23-19.

And Smith added: "With South Africa there is a consistent level of physicality. You can't catch them on an off-night, and in the past five years it's always been tight when we have played.

"They are always tight match-ups with the Springboks, and I am sure this one will be the same. They've been impressive so far, and individually they have great players.

"Although we beat them in our last outing in the Rugby Championship, we weren't proud of the way we played. We know we are playing a very good, physical side.

"Their performances so far suggest they will be better at the set-piece than France, and our defence will have to be on top of its game.

"The strengths of South Africa will be different to those of France, and so will the threats.

"The nerves are different at a World Cup, and that is when you know a big game is on the way.

"You have to make sure you are getting your preparation right and analysing the opponents as much as possible."

All Blacks head coach Steve Hansen will name his team for the Springboks game on Thursday, with loosehead prop Wyatt Crockett the main fitness concern.

Crockett suffered a groin injury and went off to be replaced by Joe Moody just 28 minutes into the France match.