Jose Cifuentes's first-half screamer helped Ecuador outpace the USA 2-1 and reach their first semifinals at a Fifa Under-20 World Cup.
La Tricolor struck first and with purpose at Gdynia Stadium. Cifuentes's thunderous, right-footed effort from 25 yards left USA goalkeeper David Ochoa grasping at air as the ball seared the back of the net.
The Stars and Stripes were not behind for long. Tim Weah volleyed past Moises Ramirez from close range in the 36th minute following Alex Mendez's corner kick. It was Weah's second goal at Poland 2019.
As the game began to open up, the South American holders retook the lead through Jhon Espinoza just before halftime.
The defender was rewarded for his run through the middle of the penalty area when he connected with Leonardo Campana's centreing pass to score, giving his side a 2-1 advantage in the 43rd minute.
Sebastian Soto earned the USA's best chance to draw level in the second half. Substitute Uly Llanez picked Soto out lurking at the far post, but Ramirez charged off his line to force the USA goalscorer's shot off target in the 58th minute.
Though the reigning CONCACAF winners reached their third consecutive quarterfinals they have been unable to advance past that stage each time.
Ecuador will travel to Lublin for their first semifinal on 11 June.