Defending Olympic women's hockey champions the Netherlands and hosts Great Britain secured contrasting wins on Thursday to boost their semi-final prospects at London 2012.
In Pool A, the Dutch edged past China 1-0 in a repeat of the 2008 final, while Britain outplayed Belgium 3-0.
Both teams have nine points from three matches, but Britain lead the table with a superior goal difference.
China, the third placed team in the pool, have four points from three matches.
World champions Argentina bounced back into semi-final contention after Tuesday's loss to the United States when they defeated New Zealand 2-1 Pool B.
Carla Rebecchi scored both goals for Argentina in open play, in the third and 45th minutes, while New Zealand's Charlotte Harrison reduced the lead in the 62nd.
Argentina's victory gave them six points from three matches and resulted in a four-way tie in the group.
Australia, Germany and New Zealand also have six points each from three games.
Australia moved back into the race for semi-finals with a hard fought 1-0 win over United States.
They scored four minutes after their goalkeeper had saved a USA penalty stroke. USA have three points from as many matches.
Germany defeated South Africa 2-0 to keep alive their chances of advancing to the semi-finals.
Marie Mavers deflected in a diagonal pass in the 25th minute and German captain Fanie Rinne shot home on a penalty corner in the 44th.
Maartje Goderie scored the match winner for Netherlands in the 10th minute by beating the goalkeeper with a shot just inside the far post. This was the first goal conceded by China in three games.
Dutch captain Maartje Paumen, who was a member of the gold medal-winning team in 2008, said: This was a new game and had several new players.
"China is a good side, but we pressed and created chances. I remember we pressed hard in the 2008 final also," said Paumen.
Max Caldas, coach of the Netherlands team, said he was happy with the maximum nine points from three games.
"We did not score many goals, but I am happy with three victories," said Caldas.
Meanwhile Britain took a long time to convert their dominance into goals against Olympic Games newcomers Belgium.
Ashleigh Ball opened the scoring just before half-time. Laura Bartlett spun well to add a second goal and Crista Cullen completed the scoring with a low penalty corner flick.
Kate Walsh, the Great Britain captain who fractured her jaw four days ago, came back to join the team bench after surgery.
No decision has yet been made if she will be able to play again in these Olympic Games.
Anna Flanagan scored Australia's goal in the 33rd minute with a strong flick at a penalty corner.
Lauren Crandall, the USA's experienced captain, took her team's 29th minute penalty. It was a good flick, but Australian goalkeeper Toni Cronk produced an even better save.
Adam Commens, the Australian coach, praised Cronk for "a number of outstanding saves today".
South Korea won the early morning game against Japan 1-0, without conceding a single penalty corner, to get off the bottom of the Pool A table.
Their decisive goal came from a corner conversion by Cheong Seul Ki in the 42nd minute.
Lee Seon Ok, the South Korean captain, said: "Cheong scored in the upper left corner. She shot high because the Japanese goalkeeper is quite short."