Amad Diallo scored in the 90th minute to lift Ivory Coast, making their first World Cup appearance in a dozen years, to a 1-0 victory over Ecuador.
The teams combined to hit the crossbar three times in Philadelphia on Sunday (Monday AEST), before the Manchester United winger - who entered as a substitute in the 56th minute - broke through with a left-footed shot from just inside the penalty area that beat diving goalkeeper Hernan Galindez.
Wilfried Singo set up the goal with a strong run down the right side.
Making their fourth appearance in the World Cup and first since 2014, Ivory Coast took a step towards reaching the knockout stage for the first time.
Ecuador saw their 19-game unbeaten streak end with their first loss since a 1-0 decision against Brazil on September 6, 2024.
