Mexico's Claudio Zamudio scored in the first half, before Bryan Salazar's penalty after the break saw off Ecuador with a 2-0 win.
The Mexicans were swift out of the blocks, controlling the ball well and attacking Ecuador dangerously in the opening moments. Most notably Eduardo Aguirre came within inches of opening the scoring within the first minute after a cross-shot flashed wide.
Ecuador began to grow in stature, though with the electric Jhon Pereira breaking free of the Mexican defence before hitting a toe-punt shot which Abraham Romero got down to turn round the post.
It was the two-time U-17 World Cup champions who took the lead though, with Zamudio slotting home from inside the penalty area after Salazar nodded down a deep free-kick.
El Tri doubled their advantage just after the interval when No20 fouled No20 in the Ecuadorian penalty area. Jean Pena brought down Mexican substitute Jose Gurrola, and Salazar stepped up to slot past Jose Cevallos in the Ecuador goal.
Meanwhile, Belgium booked their place in the final four with a 1-0 win over Costa Rica.
The Red Devils then went ahead thanks to a moment of technical excellence from Rigo. Steve Ryckaert stepped over the ball and the number eight curled an unstoppable set-piece past the despairing Barrientos.
Belgium then took control of the remainder of the opening period, despite Costa Rica looking dangerous on the counter attack.
Costa Rica went closest to levelling late on. A long ball was deflected into the box and Teunckens could only palm the looping ball onto the post which deflected back into the penalty area. Pablo Arboine fired wide with the goal gaping. Teunckens then showed remarkable reflexes to claw out a deflected Arboine free-kick.
Semi-final fixtures:
Mali v Belgium
Mexico v Nigeria
