AUCKLAND: Serbia advanced to its maiden Under-20 World Cup semifinal Sunday with a 6-5 win on penalties over the United States.

The match needed 18 penalties to decide a victor after it finished 0-0 at fulltime, and in the end it was Serbia that advanced after a marathon shootout.

Serbia's defense restricted the United States to two shots on target, as Serbia maintained its impressive defensive record which has seen it concede just two goals throughout the tournament.

For the United States, the chance to match its best effort at the tournament since 1989 was dashed despite the efforts of goalkeeper Zackary Steffen.

Serbia will play Mali at Auckland on Wednesday after the Africans upset Germany 4-3 on penalties in Christchurch in Sunday's earlier quarter-final.

A fairly equal first half meant there were limited chances for either side, but the best opportunity fell to the United States four minutes from half-time.

A delightful run down the left hand side resulted in a low cross to Thomas Thompson in the box, but his effort was inches wide of Serbia goalkeeper Predrag Rajkovic's far post.

The match opened up in the second half, and after 57 minutes a neat cross found Andrija Zivkovic at the far post, but his first-time volley swept across Zackary Steffen's goal.

Steffen was called into action soon after and pulled off a stunning save to deny Zivkovic for a second time in 12 minutes.

Serbia looked to have had the US on the ropes early in extra time, but Ivan Saponjic's deflection from a Stanisa Mandic cross went wide.

From there the match went to penalties, where Serbia clinched its first semifinal berth after a shootout to the delight of the vocal Serbian supporters.