The Red Bull Salzburg midfielder, who scored 15 goals in 83 appearances for his country, feels it is time to let younger players take centre stage.

"It was a difficult decision because to play for my country means everything to me," the 37-year-old told Zagreb daily Vecernje Novosti.

"But I am not a young lad and I know that it would be a burden on the national team if I continue, given that I don't even play regularly for my club.

"Croatia face a tight battle to qualify for the 2010 World Cup finals and the team needs younger players who play every week for their clubs.

"We have several players in my position and coach Slaven Bilic has plenty of options."

Kovac, who has only played 11 times for Salzburg this campaign, also revealed that he will consider hanging up his boots for good at the end of the season.

Bilic said the former Bayern Munich and Hertha Berlin midfielder will be sorely missed.

"His retirement is a big blow to our hopes in qualifying for the World Cup," he said. "Niko deserves all the credit for what he has done for the national team and players like him are indispensable."