The young Taeguk Warriors are paired with Argentina, England and Guinea in Group A at the 24-team competition.

Paik and Lee have been core players for the U-20 squad. They're joined by defender Jeong Tae-wook, who lost consciousness during a friendly last month but was still able to get his name on the roster.

Four players -- Shin Chan-woo, Kim Jeong-hwan, Kim Jung-min and Kim Jin-ya -- failed to make the cut from Shin's 25-man provisional squad that was announced earlier this month.

"I picked the players based on their talent," Shin said through the KFA. "Since we can only take 21 players, for certain positions, I had to choose versatile players. I'm sorry for the four players who couldn't be with us even though they worked hard with the team."

Shin has been working with 25 players since April 10 and had four friendly matches before announcing his final entry for the U-20 World Cup.

"We focused on improving our stamina, and I'm satisfied with our work," he said. "Although the players might feel fatigued and not fit for the match, I'm sure they will reach their best form when the tournament begins."

The 21 players will re-assemble on Monday at the National Football Center in Paju, north of Seoul.

"From next week, we will improve our ability to execute tactics," he said. "We will train on details such as pressing tactics and attacking strategies to dismantle the opponent's defense."

South Korea will have three tune-up matches before entering the World Cup. They will first meet Saudi Arabia on May 8 in Paju, and will go head-to-head against Uruguay on May 11 and Senegal on May 14. Uruguay and Senegal will also compete at the U-20 World Cup.

"We will play friendly matches to raise the form of our team," he said. "But if we have injured players, that's a huge loss. I hope those situations will not happen." (Yonhap)