Three fine second-half saves from goalkeeper Sergio Romero kept Argentina level heading into injury time, while Iran also had a strong penalty appeal waved away when Pablo Zabaleta appeared to foul Ashkan Dejagah inside the area.
However, despite having endured a quiet game by his standards, Messi produced a moment of magic when his side needed it most to register his second goal of the tournament.
Argentina now lead Group F with maximum points from two games and will be confirmed as group winners should Saturday’s late game between Nigeria and Bosnia Hercegovina fail to produce a winner.
Coach Alejandro Sabella resorted to the 4-3-3 system preferred by Messi with the four-time World Player of the Year joined by Gonzalo Higuain and Sergio Aguero in attack.
However, despite enjoying the vast majority of possession in the first-half, La Albiceleste struggled to create chances from open play against a well-organised Iranian defence.
The first opening fell to Higuain from a fine pass by Fernando Gago, but Iranian ‘keeper Alireza Haghighi bravely smothered the ball at the Napoli striker’s feet.
Angel di Maria and Messi from a free-kick then fired over from the edge of the area, but Argentina were having some joy from set-pieces and Marcos Rojo and Ezequiel Garay should have done better when they failed to hit the target from close range from fine deliveries by Messi.
Iran were also dangerous from set-pieces, though, as they could even have gone ahead before the break when Jalal Hosseini headed just over from a corner.
It was the Asian side who threatened again at the start of the second period as Reza Ghoochanneijhad forced a fine low save from Romero with a flashing header at the near post before Dejagah’s appeals for a penalty were turned down when he tumbled in the area under pressure from Zabaleta.
Messi then had his first clear chance of the game as he raced onto Javier Mascherano’s pass but curled the ball just wide of the target.
Romero was forced to come to his side’s rescue again moments later he got fingertips to a fine header from Dejagah to turn the ball behind and the Monaco stopper denied Reza once more as Iran threatened to nick all three points on the counter-attack two minutes from time.
Instead it was Argentina who snatched victory at the last as Messi created the half yard of space he needed on the edge of the area before leaving Haghighi with no chance as he curled the ball just inside the far corner on his favoured left foot. – AFP