Filed at 7:46 a.m. ET ANAHEIM, Calif. (AP) -- Hee-Seop Choi's three-run homer off Dan Wheeler in the fourth inning was the key blow Monday night as South Korea beat the Americans 7-3 to remain the only unbeaten team in the inaugural World Baseball Classic. The game was played before an announced crowd of 21,288 at Angel Stadium. ''When they got a good pitch to hit, they didn't miss it,'' Team USA manager Buck Martinez said. ''They pitched very effectively to the heart of our order. We hit some balls hard. They made quality pitches when they had to.'' South Korea (2-0) will play its final game of Round 2 against Japan on Wednesday night. Japan (0-1) will face Mexico (0-1) on Tuesday, and Team USA (1-1) will play Mexico on Thursday in other Round 2 action. The top two teams will meet Saturday in the semifinals at Petco Park in San Diego. South Korea led 3-1 when Min Jae Kim, who had three hits, doubled with two outs in the fourth. Seung Yeop Lee was walked intentionally before Choi hit a towering fly ball into the right-field corner that barely eluded Vernon Wells, landing just fair and in the second row, making it 6-1. Lee put South Korea ahead for good by hitting his WBC-leading fifth homer off Dontrelle Willis in the first. Lee came to the plate in the fourth with seven hits in 15 at-bats, seven runs and 10 RBIs in the Classic, making the decision to walk him seem reasonable. But Choi, a Los Angeles Dodgers' reserve pinch-hitting for Tae Kyun Kim, spoiled the strategy. ''Lee has been red hot in this tournament,'' Martinez said. ''I just felt like it was the best move. I felt like we would take our chances. Hee-Seop Choi, we knew him very well. We just didn't get the ball in on him. He got enough of it to hit it over the fence.'' The Americans didn't play anywhere near their best. They put the first two runners on base in the first, fourth and fifth innings, but failed to score each time. They stranded 11 baserunners and committed three errors after making only one in the first four games. ''We definitely could have played better,'' said first baseman Mark Teixeira, who went hitless in four at-bats with two strikeouts. ''Anytime you lose, there are things you could have done better. ''We could have hit better, we could have fielded better, we could have pitched better. But they just beat us.'' Team USA's problems started with Willis, who had his second bad outing of the Classic, giving up four hits, four walks and three runs in three innings. ''I just had bad rhythm today,'' he said. ''I think I was very composed out there. I had a great game plan, I just didn't execute. I'm just not playing the best baseball I can possibly play. My confidence is still up.'' Martinez said he hasn't lost confidence in the Florida Marlins left-hander. ''I don't think there's a man in that clubhouse who doesn't want to give the ball to Dontrelle Willis,'' Martinez said. ''It's just a matter of giving him one more chance. We're going to do everything we can to give him the ball.'' Choi, who hit three homers in a game against Minnesota last season, said this one was more meaningful. ''This is different -- it's for my own country,'' he said through a translator. ''And we were able to beat the U.S., which is the best team in the world.'' South Korean manager In Sik Kim seemed surprised by his team's convincing victory. ''Something happened today which nobody could believe,'' he said. ''This is a collection of all the best of the major league players. It's very difficult to believe what happened. But this is baseball. You never know what might happen.'' Derek Jeter and Ken Griffey Jr. had three hits each for Team USA. Griffey hit his third homer of the Classic and drove in two runs. After Lee's two-out homer in the first, the winners got another run on a walk and singles by Ji Han Song and Bum Ho Lee. Griffey homered with two outs in the third off Min Han Son, but Japan countered on Bum Ho Lee's RBI grounder in the bottom of the inning. Kim's run-scoring single off Mike Timlin in the sixth made it 7-1. The run was earned despite two errors in the inning by second baseman Chase Utley, who was booed when he came to the plate to lead off the seventh. Team USA scored twice off Tae Hyon Chong in the ninth on a run-scoring single by Griffey and an RBI grounder by Alex Rodriguez before Seung Hwan Oh retired Chipper Jones on a grounder to second to end the game. Son allowed two hits and one run in three innings in his second effective outing of the Classic. Reliever Dae Sung Koo pitched three shutout innings for South Korea. ''We had our chances right from the first inning,'' Jeter said. ''We just didn't get any hits with guys on base. I don't know if you can learn from it. I'm well aware of what it takes to win. We just didn't do it.'' More Articles in Sports