A late try from right wing Ben Smith helped New Zealand to a 33-15 bonus-point win over Argentina on Saturday.
That critical fourth try puts the All Blacks five points clear of the Springboks ahead of the two team's meeting at Ellis Park in Johannesburg next week.
South Africa know they must beat New Zealand with four tries or more whilst also denying their hosts a losing bonus-point. It is a tough ask.
It had looked like being an extremely tough night for the All Blacks though when the Pumas enjoyed the better of the opening sparring. New Zealand were struggling to get their hands on the ball.
Marcelo Bosch had an opportunity to draw first blood when his 55-metre penalty attempt sailed well wide. However, Argentina weren't to be denied in the eighth minute as Nicolas Sanchez sent over three points following Andrew Hore's high tackle. It was a lead they richly deserved.
New Zealand responded five minutes later as Argentina failed to release the tackler so up stepped Aaron Cruden - in ahead of the Beauden Barrett and the injured Dan Carter - before the lead was Argentina's again in the sixteenth minute. Fly-half Sanchez was looking in good shape from the kicking tee at close range.
With a quarter of the game gone came another plus point for the Pumas - and in fact the watching Springboks - as Juan Figallo dominated Tony Woodcock at scrum time. In fact Marco Ayerza would do the same to Owen Franks later in the half - after Sanchez's first miss.
But as is New Zealand's wont, they struck when given a sniff. It was Julian Savea who profited as he snaffled up the loose ball before racing in for the game's first try. Unfortunately for the visitors, Cruden was off-target. Unfortunately for rugby, the fan with a laser was not.
Cruden did extend the advantage to five points just before the half-hour when the Pumas joined a ruck incorrectly, but then came Leicester prop Ayerza's moment at the set-piece. Net result being that Sanchez had brought his side back to a 9-11 deficit at the break.
An indication of the Pumas' scrum dominance could have been signalled by Franks being replaced at half-time by Charlie Faumuina. But worryingly for New Zealand was the sight of the replacement prop being pinged at his first set-piece. Bosch was successful this time.
11-12 didn't last long though as Cruden landed three points of his own before the All Blacks found top gear. Their second try arrived following solid tight work from the pack before the ball was shipped wide by Cruden and Ma'a Nonu to the waiting Sam Cane on the left wing.
Two became three in a short space of time as New Zealand had turned the screw at Estadio Ciudad de La Plata. Their next score en route to the bonus-point saw Nonu again act as the provider, sending off a lovely pop pass to wing Smith off the shoulder in midfield. The winger raced over from 35 metres making for a simple conversion for Cruden.
New Zealand were now in full control of the Rugby Championship game as the Pumas' fitness combined with the superior mental strength of the All Blacks came to the fore.
And just when it looked like the fourth try was not coming, up stepped wing Smith as he barged over the would be tackler en route to the uprights for the vital bonus point.
Man of the match: Constantly looking for work while being smart when in possession, Ben Smith takes this ahead of namesake Conrad due to his two scores. Meanwhile Ma'a Nonu impressed at inside centre, as did the Pumas props Juan Figallo and Marcos Ayerza.
Moment of the match: It has to be Ma'a Nonu's double pump pass for Ben Smith's first try. The pass was a beaut and came after Nonu had driven back an Argentine in an earlier phase. He really is a different player from Super Rugby when he pulls on that Black jersey.
Villain of the match: The fan(s) with a laser pen.
Pen: Sanchez 4, Bosch
For New Zealand:
Tries: Savea, Cane, B Smith 2
Con: Cruden, Barrett
Pen: Cruden 3
Argentina: 15 Juan Martín Hernandez, 14 Lucas Gonzalez Amorosino, 13 Marcelo Bosch, 12 Santiago Fernández, 11 Juan Imhoff, 10 Nicolás Sanchez, 9 Martin Landajo, 8 Juan Manuel Leguizamon, 7 Pablo Matera, 6 Juan Martín Fernández Lobbe (captain), 5 Patricio Albacete, 4 Julio Farias Cabello, 3 Juan Figallo, 2 Eusebio Guiñazú, 1 Marcos Ayerza.
Replacements: 16 Agustin Creevy, 17 Nahuel Lobo, 18 Juan Pablo Orlandi, 19 Mariano Galarza, 20 Benjamín Macome, 21 Tomas Cubelli, 22 Felipe Contepomi, 23 Horacio Agulla.
New Zealand: 15 Israel Dagg, 14 Ben Smith, 13 Conrad Smith, 12 Ma'a Nonu, 11 Julian Savea, 10 Aaron Cruden, 9 Aaron Smith, 8 Kieran Read, 7 Sam Cane, 6 Liam Messam, 5 Sam Whitelock, 4 Brodie Retallick, 3 Owen Franks, 2 Andrew Hore, 1 Tony Woodcock.
Replacements: 16 Kevin Mealamu, 17 Wyatt Crockett, 18 Charlie Faumuina, 19 Jeremy Thrush, 20 Steven Luatua, 21 Tawera Kerr-Barlow, 22 Beauden Barrett, 23 Charlie Piutau.
Referee: Jaco Peyper
Assistant referees: Nigel Owens (Wales), Pascal Gauzère (France)
Television match official: Graham Hughes (England)