A single, mischievous South Korean flag was held aloft in the east stand at Old Trafford during the national anthems and, as a sombre North Korea coach Sin Ui-gun illustrated afterwards, this clash of ideologies was never going to be restricted to football tactics. "We all think that when we play the United States we shouldn't lose, we should win," he lamented. "That is what we normally think." Asked if this hurt more than a preceding 5-0 drubbing by France, he replied simply; "Yes."

Even against a USA team defending their Olympic title there can be no consolation in defeat for North Korea but, in the context of a football game at least, they should be grateful the reverse was not more emphatic. "It was a difficult game with North Korea having five at the back," said the USA coach, Pia Sundhage. "But we chose to slow the game down in the second half to save our legs for the quarter-final."

Elvis Costello's Pump it Up had reverberated around Old Trafford at half-time and presumably was a reference to the noise levels from a crowd of 29,522 rather than hostilities between the competing nations. The United States has never diplomatically recognised North Korea but, with the correct flag on show – officially at least – and the game able to kick off on time as a result, there was no mistaking their opponents' limitations. It was not a member of the axis of evil they had to overcome in Manchester but a North Korean football team offering minimal threat.

North Korea needed to avoid defeat against the USA, or rely on results elsewhere, to reach the quarter-finals and began the game with damage limitation as priority. This was always a dangerous policy against a nation that have won gold in three of the past four Olympics, that qualified with a 100% record and scored seven goals in their first two appearances at London 2012, mind.

The flow of the game was established immediately with Chang Ran-o, the North Korea goalkeeper, forced into two near-post saves from the USA's opening attacks. A neat turn and shot from the edge of the area by Alex Morgan, admittedly aided by nonexistent defending, struck a post and a procession appeared in store when she created the breakthrough for Abby Wambach 10 minutes later. Collecting a lofted pass into the area from Carli Lloyd, the USA striker resisted the temptation of a first-time shot and guided an intelligent pass between two North Korea defenders for Wambach instead. Her strike partner guided home a simple finish from close range.

Chang Ran-o denied Wambach a second and the USA goalscorer also hit the post when she threw herself at a deflected shot, but there was a wastefulness to the defending champions that spared North Korea. Lloyd sliced over from a good position, the substitute Tobin Heath chipped over the bar with only the keeper to beat and Sundhage, captured on television shaking her head several times, was clearly annoyed with a laboured approach.

"I should be more careful with my body language in future," said the USA coach, when informed that she had been caught on camera. "It is tough with only two days in between matches and with the travelling. We had chances and could have passed the ball better at times but to win 1-0, to keep a clean sheet and reach the quarter-finals, I shouldn't have shook my head."

Any faint hopes that North Korea possessed of a late equaliser were extinguished when the substitute Choe Mi-gyong was sent off for two bookable offences in quick succession.