Argentina's Lionel Messi had a penalty saved by Iceland goalkeeper Hannes Por Halldorsson, but strike partner Sergio Aguero says the team will continue to support him, and the miss shows he is human.
Iceland made a stunning first-ever World Cup appearance when they held 2014 runners-up Argentina to a 1-1 draw in a dramatic match.
Aguero had given the twice world champions the lead after 19 minutes of the Group D match. However, Iceland showed exactly the same commitment and self-belief as when they stunned the world with their run to the quarterfinals of the European Championship two years ago and hit back four minutes later through Alfred Finnbogason.
Argentina eventually took command and delivered wave after wave of attacks in the second half, but they actually created few clear chances on either side of the poorly struck 64th-minute penalty by Messi, who had a remarkable 11 shots during the match.
"The first match is always the most difficult. Everyone wants to play against us," Aguero told TyC Sports. "They were defending; their only chances to score were from a set piece or looking for the second play. I think they celebrated the draw as a victory.
"Leo showed he's human. We support him. He just had a bad day, but we know that he can give us the victory at any moment of the game. I hope he can be better for next match against Croatia."
Defender Javier Mascherano added in the mixed zone: "We have to move on. This has just started, and we can't allow ourselves to fall down. They used a lot of people to defend, and it wasn't our best day. They have just one chance and a half in the whole game, and they scored."
And Argentina coach Jorge Sampaoli said: "We need to find more variety of options going forward. It's a very competitive group.
"The circumstances around the missed penalty and that led to Leo's mistake, that's just another statistic, it's part of the past. ... Football is like that. We need to be strong as a group, believe in ourselves and know we have all the tools to beat anybody."
Argentina legend Diego Maradona posted on Instagram after the game: "I started la World Cup with a loss, not a tie. It was in our first game in Italy '90. And despite the injuries, despite everything, we reached the final, thanks to Goyco and the sacrifice of all the boys. Let's keep supporting the team. LET'S GO ARGENTINA!!!"
Iceland, by far the smallest country by population to appear at the World Cup, famously beat England in the round of 16 of Euro 2016 and again, inspired by their "thunderclapping" fans, ran tirelessly and fought for everything to write another glowing chapter in their short but glorious major tournament story.
"I hope it is going to prove important to us to reach our goal to qualify," Halldorsson said of the penalty save. "I did my homework. I looked at a lot of penalties by Messi, and I also looked at how I had been behaving in previous penalties, so I tried to get into their mindset, how they would be thinking about me.
"I think the Argentinians felt a bit frustrated that they weren't getting through, and it was important we equalised so quickly. I guess our game plan worked almost perfectly."
Information from Reuters was used in this report.