Argentina is the firm favorite to win its sixth Under-20 World Cup after edging highly touted Mexico, 1-0, in the quarterfinals on Sunday in Ottawa.
Maximiliano Moralez scored Argentina's winning goal just before halftime on a shot that deflected off Mexican Julio Cesar Dominguez. Mexico's best chance came in the first half when star Carlos Vela hit the post.
Argentina meets Chile, a 4-0 winner over Nigeria in overtime, in one semifinal.
Austria, which upset the USA, 2-1, in overtime, faces the Czech Republic, which eliminated European champion Spain in a shootout after their game ended 1-1.
Austria 2 (Okotie 43, Hoffer 105) USA 1 (Altidore 15) (OT).
Czech Rep. 1 (Kalouda 103) Spain 1 (Mata 110) (OT).
(Czech Rep. wins 4-3 on penalties.)
Chile 4 (Grondona 96, Isla pen. 114, 118, Vidangossy 120) Nigeria 0.
Argentina 1 (Moralez 45) Mexico 0.