CHENGDU, China -- The American women are about to meet soccer's "mystery" team.That's North Korea, which the United States faces on Tuesday in its opening game of the three-week World Cup. Just as reclusive as the rest of the country, only a few U.S. players have faced Asia's top team and FIFA's No. 5-ranked side. And that was four years ago -- when the Americans won 3-0 -- in the last World Cup. In the only other game between the two, the U.S. also won 3-0 in the 1999 World Cup. "No one has seen them play, so it's very easy for the reputation to keep growing and growing and growing about how good they are," defender Kate Markgraf said. "That has to be based on something." North Korea and the top-ranked United States make up half of Group B -- the toughest in the tournament -- with No. 3 Sweden and African champion Nigeria completing the foursome. The top two teams reach the quarterfinal, with the final set for Sept. 30 in Shanghai. Defending champion Germany is favored in Group A, Norway in C, and Brazil, Denmark and China are expected to tussle in Group D. "They do have this amazing reputation, it's almost like a ghost I feel like," Markgraf added. "You've heard about amazing they are, and we all just antsy to try to play against one of the best teams in the world and see how we do." The American are favorites to win their third World Cup to go with titles in '91 and '99. They are undefeated in 46 games (39-0-7) under coach Greg Ryan. The only blemish in 2½ years was a penalty-kick loss to Germany in the 2006 Algarve Cup. The game was 0-0 after regulation and extra time. Because it was decided on penalties, it goes into the record books as a tie. North Korea and Sweden could ruin the party, with Sweden coming up in the second game on Friday. The final group match is against Nigeria in Shanghai. "I think we are prepared for as many possibilities as there are," Markgraf said. "We haven't thought about losing, but yet we know that is always out there." The U.S.-North Korea matchup may be the best of the 16-team tournament. Both teams attack relentlessly, their defenses are organized and North Korean striker Ri Kum Suk is a match for American strikers Abby Wambach and Kristine Lilly. "She's a true superstar player," Ryan said of Ri. "She has the same kind of impact on her team that Abby Wambach and Kristine Lilly have on our team. She's great on the dribble, great in the air like Abby and she creates like Lil." Ryan has been preaching about North Korea to his relatively young team, which is likely to start five players who have not played in a World Cup. "We know they are very quick, they turn on a dime," defender Christie Rampone said. "They are definitely a counterattacking team that tries to catch you sleeping." Wambach is America's go-to striker, a natural finisher with 77 goals in 96 games. Alongside is 36-year-old Lilly, who played in the inaugural World Cup in '91. She's played in 331 games, scored 126 goals and is the only player who has competed in every women's World Cup. That will be five, and only two men can match that: Mexico's Antonio Carbajal and Germany's Lothar Matthaus. She's also played in every U.S. World Cup game and in every Olympic gold-medal game. Stalwarts like Mia Hamm, Julie Foudy and Brandi Chastain retired after the United States won gold in the 2004 Olympics. Lilly is the old link on a younger team looking for its own identity. "We're anxious for the first game," Lilly said. "The nerves are going to be there. They are going to be there for me, even though it's my fifth. I haven't seen a difference compared to the younger ones. I'm just as excited as they are."