The US will face either Cuba or South Korea
John Gall hit a home run to help the United States beat Taiwan 4-2 and ensure their place in the Olympic baseball semi-finals.
Dexter Fowler, batting ninth, hit a single, double and triple for the US, who will now face either Cuba or South Korea in the last four.
Japan cruised to a 10-0 win in seven innings over hosts China.
Tsuyoshi Nishioka hit a two-run homer and also singled while Hideaki Wakui struck out six and allowed two hits.
Ko Young-min's two-run single in the fourth and Cuba's costly two-run error in the same inning gave South Korea a 7-4 victory over defending champions Cuba.
South Korea is 6-0 and the only remaining undefeated team with one group game left.