New Zealand will be overwhelming favourites when they play France in Sunday's World Cup final, a repeat of the inaugural 1987 match-up that the All Blacks won.

But All Blacks coach Graham Henry warned that he would not underestimate a French side he said could be "the best in the world on their day", despite having already beaten them 37-17 in a pool match at this tournament.

"We don't underestimate the ability of France," Henry said on Monday.

"Although France didn't play well in their semi-final (the French just held on for a 9-8 win against 14-man Wales), we know they have the ability to play outstanding rugby."

Henry knows that better than most, having survived calls to be sacked after New Zealand's 20-18 World Cup quarterfinal loss to France in Cardiff four years ago.

"Over the last eight years, we've lost once at home in Dunedin, and won all our games away apart from that quarterfinal in the 2007 World Cup - that's the most bizarre game I've been involved in.

"But they (France) will be no more difficult to prepare for than Australia. It's a question of building in the week," Henry said, adding: "There'll be subtle changes in the game plan.

"France can be the best in the world on their day."

Meanwhile cross-code star Brad Thorn, for whom the final is set to be his last outing in an All Blacks shirt, quoted advice from Wayne Bennett, his former coach at Australian NRL rugby league club Brisbane Broncos.

"He used to say that one of the hardest things is getting to the final," veteran lock Thorn recalled.

"Do you think anyone's going to remember who won a semifinal in 2011? No one's going to care. It's all about what happens this weekend."

New Zealand advanced into the final on the back of a commanding 20-6 win over Australia here on Sunday.

"It was a great game, a heroic performance that everyone contributed to, and it was very pleasing in that respect," said Henry.

"Our kicking game was good at times but we could improve on that," he added having seen his side miss several shots at the posts.

"It was a big game because there's a bit of history and then there's the need to get into a World Cup final.

"It's been 24 years since the All Blacks have won a World Cup.

"The supporters knew it was a big step in the right direction getting through this game."

Henry added: "Australia are a very good side and they've got players, especially in their backs, who can you to pieces and win rugby games against the odds."

New Zealand may be a rugby 'superpower' but they've won the World Cup just once and former Wales coach Henry said his approach to the tournament had changed from four years ago.

"In 2007 we took it one game at a time," he said. "This year, we dissected the World Cup and its history and looked at why the All Blacks have not won in 24 years, and we used that to give us more knowledge.

"It's a new experience for this group (to get this far). It's very important we come down after the semifinal, get to base again, have a clean sheet of paper and build again.

"If we do it too early, that leads to anxiety."

Reflecting on the injury toll from Sunday's clash with the Wallabies, Henry said centre Ma'a Nonu, who scored the only try of the match, had suffered a neck strain with reserve scrumhalf Andy Ellis and wing Cory Jane both sustained knocks to their noses, while first-choice number 9 Piri Weepu was battling a virus.

But Henry said all the fitness issues were "nothing serious".

AFP