Maximiliano Moralez scored the lone goal in first-half injury time as Argentina kept alive its bid for a second consecutive title at the Under-20 World Cup with a 1-0 quarter-final victory over Mexico.
It was Argentina's second victory over Mexico in an international competition in five days after the senior side beat El Tri 3-0 in the semifinals of the Copa America on Wednesday.
The 1.60-meter Moralez scored the biggest goal of the tournament for his country so far. His shot from the top of the penalty area took a deflection off a defender and wrong-footed Mexico goalkeeper Alfonso Blanco just before half-time in an entertaining match played before a capacity crowd of 26,500.
Argentina moved a step closer to adding to its record five titles at the tournament, although it wasn't easy against a Mexican side that was in part formed from the team that won the U-17 World Cup in 2005.
Argentina, which has allowed only one goal in five games, next faces Chile in the semifinals on Thursday at Toronto's BMO Field after the Chileans beat Nigeria 4-0 in extra time earlier on Sunday at Montreal.
Austria and the Czech Republic face off Wednesday in Edmonton in the other semi-final.