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 frontman 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. 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.

Gritty Iran

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.

"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."