Lionel Messi saluted Argentina's character and determination, insisting they "strengthened" following his penalty miss to secure their crucial 2-0 World Cup win over Poland.

Lionel Scaloni's side booked their place in the last 16, bouncing back from Wojciech Szczesny saving Messi's spot-kick with second-half goals from Alexis Mac Allister and Julian Alvarez sending them through as Group C winners.

La Albiceleste, who suffered a shock 2-1 defeat to Saudi Arabia in their opening match, have now reached the World Cup knockout stages for the 13th time in 14 appearances, and will play Group D runners-up Australia on Sunday.

"The team came out strengthened after that mistake of mine," said Messi, who surpassed Diego Maradona in playing the most World Cup games for Argentina (22). 

"We knew that once the first goal went in it was going to change the game. The previous game gave us a lot of peace of mind and we went out on the pitch thinking we should win.

"The game with Australia is going to be very difficult. Anyone beats anyone, everything is very even. We have to prepare for the game in the best way we always do.

"We must be calm and go game by game. Now, another World Cup starts, and hopefully we can continue to maintain what we did today."

Nicolas Otamendi concurred: "This is a team that strengthens under pressure, it was demonstrated. Today we had a final, and we never lost focus."

While Rodrigo De Paul hailed the "personality" demonstrated by the squad, Mac Allister believes the performance will boost their belief heading into the knockout stages.

"I think today was a great team game, and that gives us a lot of confidence for what's coming," he said.

"It was a convincing performance. We look for the goal at all times. I think we went back to being the team we used to be. We handled the ball more, we had peace of mind, and we didn't despair. We played well collectively. It fills us with confidence."