But they were in no mood to take a foot off the accelerator, and their third straight win sees them finish top of the section, leaving the Koreans in third place and unsure of their fate.
USA responded to coach Pia Sundhage’s pre-game promise of attacking football from the outset of the contest. Alex Morgan and Abby Wambach looked dangerous in attack, combining well and pressing the Korean rearguard back toward their own goal.
Morgan had two chances to score inside the opening quarter-hour, but the defending Olympic champion Americans had to wait until the 25th minute to get on the scoreboard.
Morgan brought the ball down exquisitely inside the penalty area before drawing her defender out and slipping a pass across the goalmouth, where Wambach had the easiest of tap-ins. The goal, which was extravagantly celebrated, was the American women’s 50th in Olympic football history.
Wambach continued to press for the remainder of the first half, but she failed to find another breakthrough. The Asians, for their part, did not manage to put a single shot on goal in the first 45 minutes.
Tobin Heath, who entered the game to replace Megan Rapinoe at the break, had the Americans’ first chance in the second half, but her shot from close range flew up and over the bar.
Korea DPR, knowing they needed a point to help their chances of staying alive in the tournament, began to throw caution to the wind, with the Americans happy to soak up the pressure and possess the ball.
USA goalkeeper Hope Solo was called into action on several occasions, but the Asians’ charge lost momentum in the 81st minute when Choe Mi Gyong was sent off for a second yellow card. While still fighting to the get their crucial goal, the Koreans were unable to overcome fatigue and their numerical disadvantage.
Up next for the Americans, who must be considered among the favourites for another gold medal, is a last-eight clash with the third-place finisher from either Group E or F.