An extra-time winner from substitute Chioma Ubogagu has lifted USA to a 2-1 victory and into a semi-final match-up with Nigeria at the FIFA U-20 Women’s World Cup Japan 2012.

The two teams had earlier exchanged top quality goals from Vanessa Di Bernardo and Kim Su Gyong during the second half of a hard-fought encounter.

The first half was largely a disjointed affair between the 2008 finalists and, despite the high energy levels, goalmouth action proved to be in short supply.

The first sight of goal did not come until the half-hour mark with Korea DPR’s Jon Myong Hwa firing a powerful free-kick from distance, which forced goalkeeper Bryane Heaberlin to produce a full-length save.

USA came close to breaking the deadlock at the end of the first half after a back-post header from Morgan Brian, which was deflected narrowly wide of the post.

The opening minute of the second period suggested a less cagey affair as Crystal Dunn made a powerful run and shot from the left side of the penalty area, forcing a diving save from O Chang Ran.

Indeed, it proved to be positive portents for the Stars and Stripes as midfielder Di Bernardo broke the deadlock soon after the break with a spectacular 30 metre strike.

Korea DPR looked dangerous with a succession of corners and drew level as Kim Un Hwa unlocked the defence with a superb short pass on the edge of a packed penalty area, and Kim Su Gyong produced an equally clinical finish.

The full time whistle allowed USA to regroup and Korea DPR struggled during extra time to find the rhythm they had enjoyed during the latter stages of the second half.

Midway through the first period came the game’s decisive moment as substitute Ubogagu peeled off her marker at the back post and headed home a perfectly flighted Dunn cross.