In-form striker Mallory Swanson grabbed her seventh goal in five games as the United States beat Japan 1-0 in the SheBelieves Cup in Nashville on Sunday.
The Americans followed up Thursday's triumph over Canada with a second victory to leave them perfectly placed going into Wednesday's final game against Brazil.
But the US women, preparing to defend their crown in July's Women's World Cup in New Zealand and Australia, survived some late scares against a Japan side that enjoyed plenty of midfield dominance but lacked the killer touch in front of goal.
Swanson showed her confidence in front of goal yet again when she put her side ahead just before the break, latching on to a through ball from Alex Morgan and then calmly slotting past Ayaka Yamashita.
The 25,471 crowd at Geodis Park saw few chances at either end with Japan playing their well-established short passing game and the Americans struggling to break them down.
Japan fired a warning shot in the 79th minute when Fuka Nagano's effort from outside the box clipped the top of the bar with US keeper Casey Murphy beaten.
Murphy then showed great reactions to keep out a close range effort from Yui Hasegawa as Japan pushed in search of a leveller.
The Americans looked to counter on the break and Trinity Rodman found space down the right but her effort flew straight at Ayaka Yamashita.
Deep into injury time, Murphy had to come to the rescue again with an excellent save to keep out a snap-shot from Jun Endo.
Swanson, who scored twice against Canada and has found the net in each of the last five games for Vlatko Andonovic's team, said she was being rewarded for focusing on her finishing.
"This off-season, I kind of just re-evaluated my game and I think one thing was that I wasn't finishing easy chances, all of the last calendar year. So I just wanted to come into this year and just be able to finish," she said.
But Swanson conceded that her team was far from at a peak against Japan.
"This game wasn't the best performance but it's going to be like that sometimes and Japan, they're a good team. They're very technical They move off the ball very well," she said.
"So I think it's good that we're able to play them and see that we need to be more disciplined in our defending, be patient and then also we need to figure out what can we do to break them down. But sometimes though you're just going to have to grind them out."
Olympic champions Canada bounced back from their opening defeat with a 2-0 win over Brazil.
The Canadians, who are locked in a dispute with their federation over pay and conditions demanding parity with the men's team, lost their opening game 2-0 to the Americans.
But Bev Priestley's team went ahead in the 31st minute with Vanessa Gilles rising to firmly head in a corner from Jessie Fleming.
Substitute Evelyne Viens made sure of the win, doubling the lead in the 72nd minute with a shot from inside the box after Brazil had failed to deal with a corner.
But Canada goalkeeper Kailen Sheridan was busy in the final stages of the game, keeping out a header from Bia Zaneratto with her outstreched feet and then tipping a Gabi Nunes header over the bar.
The tournament concludes on Wednesday in Frisco, Texas with the US hosts taking on Brazil and the Canadians facing Japan.
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