Nani scored the only goal of the first half after a defensive error to give Portugal a 1-0 halftime lead over the United States on Sunday at the World Cup.
Miguel Veloso sent a pass into the area and U.S. defender Geoff Cameroon failed to clear it, letting the ball go past him and toward Nani. The Portugal winger then easily shot past Tim Howard in the fifth minute.
Portugal was playing with Cristiano Ronaldo on the other wing. The world player of the year has been hampered by a left knee injury, but he started the match.
With the temperature at 30 degrees C (86 degrees F) at the start, the referee paused for a break to drink in the 39th minute.
The Americans can advance to the second round with a victory, while Portugal needs a win to stay in the tournament.