Portugal's best chance came in the ninth miniute when Joao Mario had an open goal but the midfielder could shoot only wide much to the bewilderment of his teammates.
Ronaldo has been in imperious form in the ongoing quadrennial tournament, scoring four goals, including a stunning hat-trick against former champions Spain in their opening match. He has just curled one of them from just inside the box into the top corner.
Queiroz admitted it would be "a special day" facing his homeland but said friendships would be put to one side as he bids to make history with Iran.
Soccer Football - World Cup - Portugal Training - Kratovo, Moscow Region, Russia - June 24, 2018. Ricardo Quaresma scored a gorgeous three-toe curler in the first half, Cristiano Ronaldo had a penalty kick saved and Iran made a penalty of its own before almost winning the match at the end.
"We go for it, with great belief and great determination to try to win the game", Queiroz said.
But their relationship soured following a second-round exit to Spain at the 2010 World Cup, after which Ronaldo suggested Queiroz was to blame for the defeat.
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A controversial injury-time penalty given after a VAR review salvaged a draw for Iran after Ricardo Quaresma's fine goal had given Portugal the lead in a game that saw a Cristiano Ronaldo spot-kick saved.
Portugal and Spain have tied on points and goal difference after winning two games.
"I want to win, my colleague wants to win and it's going to be a tough and strong battle".
Portugal have relied heavily on Ronaldo so far in Russian Federation.
Iran v/s Portugal match will be brodcast on Sony Six and Sony Six HD. A few more goals against Iran would push Ronaldo into the lead and bolster the already sky-high confidence of the player ahead of a potential round of sixteen game against Uruguay or Russian Federation.