Mali and Japan both sprang surprises, the former coming from 4-2 behind to beat Cameroon 5-4 with a golden goal and the latter beating Portugal on penalties after a 1-1 draw.

Spain beat the United States 3-2 to join the quarter-finalists on a day which saw 21 goals in four games.

Argentina won the Youth Cup on the last two occasions, in Qatar in 1995 and Malaysia two years ago, but this time they were missing six top players because of club commitments.

They have struggled for goals and Luciano Galletti's 40th-minute header, which gave them a half-time lead in Ibadan, was only their second in Nigeria.

Mexico, who now meet Japan, overran them after the break with some dazzling play and top quality goals from Daniel Osorno, Eduardo Rodriguez, Juan Pablo Rodriguez and Luis Gonzalez. The last two were spectacular long-range efforts.

Galletti was sent off in the last minute forstamping on an opponent and a brawl was only narrowly averted. Mexico's Rafael Marquez was dismissed for his part in the arguments.

Mali, who won their first round group after beating Portugal and Uruguay, continued their run in dramatic style in Enugu.

The team from the poverty-stricken sub-Saharan nation, which has never got near qualifying for a senior World Cup, trailed 4-2 with seven minutes left.

Two of Cameroon's goals came from Gaspard Komol, who became the tournament's top-scorer with five.

But goals by Abdoulaye Camara and Mahamadou Dissa sent the game to extra time and, in the 105th minute, Dissa took advantage of a defensive mix-up to send his team into a quarter-final clash with hosts Nigeria. One player from Mali and two from Cameroon were sent off.

Portugal went out to Japan in Bauchi after playing the whole of extra time with 10 players and defender Ricardo Esteves in goal. Their regular goalkeeper Sergio Barbosa was carried off injured and Portugal had used their threesubstitutes.

The new incumbent had little to do in extra time but was powerless to stop any Japanese shots in the shootout. Japan converted all five of their penalties and went through to a quarter-final with Mexico when Pedro Costa's shot was saved.

Spain raced to a three-goal lead in Port Harcourt against the United States with two goals by Pablo Gonzalez and one by Xavier Hernandez but they then had to survive a second-half fightback.

Taylor Twellman pulled two goals back in the second half to take his tournament tally to four and he was twice denied a hat-trick by Spain goalkeeper Daniel Aranzubia. Spain play Ghana in the quarter-finals.