Club America conjured a late goal to knock Asian champions Jeonbuk Motors out of the Club World Cup and set up a semi-final with Spanish giants Barcelona on Monday.
The Mexicans dominated the first half, but were under pressure in the second before Chilean defender Ricardo Rojas' ungainly winner with 11 minutes to go.
Rojas was first into the box to meet Salvador Cabanas' cross from the right, falling on the ball under pressure from a defender as it squirmed over the line off his knees.
"It was a very tough match, the South Korean team were well organised and their movement was very quick and agile," said America coach Luis Fernando Tena.
"We'll need luck to beat Barcelona -- they're the world's number one club team, they have one of the best lineups in the world and they play great as a team."
Jeonbuk coach Choi Kang-Hee said his team almost wonit after a series of near-missesin the second half.
"Too many of our players were overwhelmed and intimidated in the first half so we didn't play well," Choi said.
"In the second half the midfielders started to move well and we had more chances. If we'd capitalised on our chances before ClubAmerica the result could have been different."
CONCACAF champions America will play favourites Barcelona on Thursday while Jeonbuk will battle it out with Auckland City to avoid last placein the competition.
Barcelona coach Frank Rijkaard was watching from the stands at Tokyo National Stadium and he will have found little to worry him in a match lacking high quality.
Jeonbuk 'keeper Kwoun Sun-Tae almost gifted America an early lead when he charged out of his area and fumbled comically, but former Valencia and Lazio striker Claudio
Lopez could not direct the rebound on target.
On-loan midfielder Fabiano had a lively start in his first match for America, firing wide from inside the box on 11 minutes and over the bar fromlong-range minuteslater.
Kwoun denied Lopez from close range after another defensive mistake while Salvador Cabanas and German Villa both shot wide before half-time.
Botti worked Jeonbuk's best chance early in the second half, challenging America goalkeeper Guillermo Ochoa on a high free-kick with Lim You-Hwan blasting his follow-up wide.
With Jeonbuk turning up the pace, Botti was denied again after 62 minutes when Ochoa parried his firm shot after a run and cut-back from Chung Jung-Kwan.
Jeonbuk came even closer when their other Brazilian import, Ze Carlo, dribbled into the box and almost squeezed a shot through the Mexican'keeper'slegs.
But Motors quickly ran out of gas when Rojas pounced in the 79th minute.
Defender Jeon Kwang-Hwan almost made it 2-0 when he cleared just inches wide under pressure from Cabanas, and substitute Juan Mosqueda blazed over the bar in injury-time.
America have two days' rest before playing Barcelona while Jeonbuk will play part-timers Auckland City for fifth place on Friday.
Jeonbuk qualified for the Club World Cup by beating Al Karama over two legs in the AFC Champions League final.
Club America are also playing in their first Club World Cup after beating Mexico City rivals Toluca to win their fifth CONCACAF title.
The competition between football's six continental champions has replaced the traditional matchup between the top European and South American clubs played since 1960.