Argentina and Australia clinched their places in the semi-finals of the women's field hockey World Cup on Monday.
Defending champion Argentina beat South Korea 2-0 to move atop Pool B on 10 points with Australia, which drew 0-0 with Japan. The US beat South Africa 3-1 for its first victory of the tournament.
Alejandra Gulla scored off a penalty corner in the 20th minute to give Argentina the lead. Three-time world player of the year Luciana Aymar scored her first goal of the championships eight minutes later.
Australia, the 2000 Olympic champions, failed to capitalize on early chances. Japan goalkeeper Rie Terazono saving with her glove a hard backhanded shot by Rebecca Sanders in the fourth minute.
The Hockeyroos continued to mount pressure with its controlled play, but couldn't break open a stubborn Japanese side looking for its first win of the tournament.
Terazono blocked a shot by Angie Skirving with five minutes remaining.
Angie Loy, Carrie Lingo, and April Fronzoni all scored for the US team, while Marsha Marescia had the lone goal for South Africa in the 44th.
"I always thought we were pretty close to putting in a really good performance," US coach Lee Bodimeade said. "South Africa is a really good side and you have to really work hard for a win."
The US have four points and will play South Korea today hoping to clinch a spot in the 6th to 8th-place playoff game.
"It's not quite as daunting a situation as it may have been in the past for us," Bodimeade said. "We're in control of it and we just have to go hard at the [South] Koreans and hopefully we'll play well."