Wales have proposed the extra match to the All Blacks' schedule should be played on November 5, just two weeks after the National Provincial Championship final on October 22.
The All Blacks, who welcome the British & Irish Lions on tour in June and July, already have matches against Ireland, England and Scotland arranged for November 12, 19 and 26 respectively but are keen to take on a Grand Slam tour of the home nations for the first time since 1978.
The New Zealand Rugby Union would prefer the match to be played on December 3 but that poses problems for Wales, who could struggle to get their first-choice players as it falls outside the recognised window for internationals, meaning clubs would not have to release their players.
Henry's worry, though, is that if the match goes ahead on November 5, he would not have enough time to prepare a side to face the Six Nations Grand Slam-winning champions.
"The biggest challenge if that date (November 5) is confirmed is that it will be two weeks to the day after the final of the NPC and there is also the considerable matter of the geography involved," he told The Dominion Post.
"There's no point in self-destructing. We want to make sure that we are going to play well and that guys will be in suitable nick to handle the Six Nations champions."
Last year the former Wales coach had just three weeks to prepare to take on World Cup champions England but Henry believes playing Wales in early November would be an even tougher task.
"Playing England at home is quite different to playing Wales, who are Six Nations champions, on the other side of the world two weeks after our NPC has finished."