“We will make it through to the next round," said the Spain midfielder, who could not find a way though a dogged Italian side in the first leg of the last-16 tie as Barca slumped to a 2-0 defeat in the San Siro.
“I would put my hand in the fire as many times as I had to for my team. I have absolute confidence that we can do it.
“We have an adverse result, it’s not good, obviously, but our mentality and our conviction needs to be that we can turn it around.
"It will be difficult but not impossible. We have to play this match as it if was a final. That’s what our mentality needs to be from the first minute to the last.
"I think the fans are confident that we can turn the tie around."
Barca would need to score four times against their fellow former Champions League holders if Milan net an away goal, but Iniesta's Barca team-mate Xavi is not running scared of the task in hand.
"We have to attack and score early," he said. "I’m fairly optimistic despite the 2-0 from the away leg.
"It’s the Champions League, our pride is a bit hurt from the unjust and excessive result from the away leg and from the two defeats to Madrid and we want to recover that sense of winning, of competing, of being a big team. There’s no better match for that than the one against AC Milan.
“We’ve played our style of football in different ways. The day we faced Spartak, we were losing and we played with three at the back.
"Perhaps Tito Vilanova has something in mind for the match on Tuesday, opening up the pitch or having a fixed centre forward, I don’t know. But we have to attack and score early.”