The United States took an iron grip on pool B while Australia and Canada are in charge of pool A after two days of the women's water polo intercontinental tournament in Auckland.
Olympic champions the US ease past China 8-2, but only after a six-goal burst in the final six minutes to break open a 2-2 deadlock.
Colleen O'Donnell, Makenzie Fischer and Kaleigh Gilchrist scored two goals apiece for the US.
''At that point it is about digging deep and finding a way to score. It takes a lot of heart when you're that tired," US coach Adam Krikorian said of the late goal burst.
Kazakhstan edged out Brazil 12-11 in a thriller, which required a penalty decider.