Lionel Messi scored a 91st-minute winner to deny Iran a surprise draw against strongly fancied Argentina in Belo Horizonte.
Two-time world champions Argentina were frustrated for long periods, while Sergio Aguero was thwarted by a great Alireza Haghighi save.
Battling Iran could have even have won it but for a brilliant Sergio Romero save from Ashkan Dejagah's header.
But Messi sent Argentina through with a fabulous late strike.