Iceland surprisingly held on for a 0-0 draw in the first leg in Reykjavik on Friday despite losing Olafur Skulason to a red card in the 50th minute, but Kovac remains confident Croatia will prevail and reach Brazil 2014.
Croatia will host Iceland in Zagreb on Tuesday and while Kovac believes his team have enough quality to triumph, the 42-year-old knows the small Scandinavian island have the ability to punish his side if they switch off.
"The impression remains that we are the better team and have a better overall repertoire," Kovac said.
"They play very simple football with a lot of vertical switching and that's always risky.
"I am confident that we will repeat our dominant display in Zagreb and will ultimately get to Brazil."
Kovac again praised Iceland's defensive work-rate in Reykjavik and hailed the performance of goalkeeper Hannes Halldorsson in keeping out the visitors in the first leg but reiterated his belief that Croatia will advance to next year's World Cup finals.
"We knew that Iceland had a strong mentality and they proved as much," Kovac said.
"Their goalkeeper also made two or three good saves. Sometimes it's more difficult to play against 10 players than against 11.
"We said before the game that we were looking to score. We didn't score but neither did they."
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