Diego Costa rejected claims he intentionally stamped on Iran goalkeeper Ali Beiranvand during a tense 1-0 win over Iran but admitted his crucial match-winner for Spain came down to “luck”.

Frustrated throughout by a dogged defensive display from the Lions of Persia, Costa courted first-half controversy when he walked towards the Persepolis shot-stopper as he prepared to kick out the ball.

The Atletico Madrid front man got so close he stood on Beiranvand’s toes, causing the ‘keeper to wince in pain and drop to the ground.

The gesture went unpunished by Uruguayan referee Andres Cunha, and Costa went on to find the net with a 54th minute strike that rebounded off the leg of defender Ramin Rezaeian.

Asked about his gesture afterwards, Costa lashed out by claiming Iran had been the main culprits.

“What game were you watching?” said Costa when probed by a Spanish journalist.

“They were provoking us, we were on the grass all the time, you can’t just say that because it’s your national team.” Costa now has three goals from two games, only one less than Portugal star Cristiano Ronaldo’s tally of four.

Ronaldo scored a hat-trick in a 3-3 draw with Spain in Sochi, where Costa scored a brace.

Costa added: “I’m not comepeting against him, (Ronaldo).” But the big Spain striker admitted his goal against Iran was fortuitous. I had a bit of luck with the goal, but I’m happy because it was a very tight game. The important thing today was to win,” he added.

Spain, looking to emulate their 2010 triumph when Andres Iniesta hit an extra-time winner to deny the Netherlands in the final, now sit top of Group B before a final match against Morocco, who restricted Portugal to a 1-0 win earlier on Wednesday.

Iran, still on three points following their opening win over Morocco, won’t give up on their “dream” of a place in the last 16, said their Portuguese coach Carlos Queiroz.

Indeed, they twice threatened to level in the second half, seeing one goal ruled offside and a late header from Mehdi Taremi go just over David De Gea’s crossbar after Vahid Amiri had nutmegged Barcelona star Gerard Pique.

“We will keep on working for our dreams, and our dream is to try and qualify for the second round,” said Queiroz.

“We know it will be difficult, but as I said before we came here and didn’t expect easy things. We lost the top spot in the group, but the reality is this: our dream is not over. Against Portugal, it will be match point for us. Portugal were up against a great Morocco team today.”