New Zealand coach Steve Hansen praised the All Blacks' resilience as they overcame a dogged Argentina side in their Rugby World Cup opener.

The defending champions started well but found themselves at a disadvantage after Richie McCaw and then Conrad Smith were both sent to the sin bin.

With the extra man Argentina pushed ahead and led 16-12 early in the second half, but New Zealand's blushes were spared as Aaron Smith and Sam Cane scored late tries to complete a 26-16 win.

"The scoreboard would reflect it was very, very hard and it took a long time to get on top," said Hansen. 

"The fact that we had two yellow cards, which were both warranted, meant we played for 20 minutes with only 14 players so that made it tougher.

"In saying that, I'm very happy with our guys, they showed a lot of attitude. 

"They haven't played for five weeks and we'll improve from that. We're on the scoreboard and can move on and look forward to our next game in confidence."

But the coach will expect a more disciplined display from his players to ensure they are not playing disadvantaged in the future.

He added: "I think the two yellow cards were pretty dumb. I have spoken to the two guys and they know they were dumb ones. 

"Sometimes in the heat of the moment, you get a little brain explosion but the rest of the discipline was pretty good. You can't afford to play with 14 guys on the track."