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.
The luckless Brazilian in the decider was Izabella Chiappini, whose effort was dropped by Kazakh goalie Alexandra Zharkimbayeva. Her team mate Aizhan Akilbayeva was the star individual performer with four goals for the winners.
In pool A, Canada sneaked past Japan in a goalfest, 15-13, while Australia were too good for New Zealand, beating the hosts 10-2.
The key passage was the second quarter, in which Australia rattled up five unanswered goals.
"Our defence was really strong and we channeled the ball really well,'' Australian goalkeeper Lilian Hedges said. ''We put pressure on the attack as showed by our score.''
New Zealand head coach Attila Biro praised his team's defensive efforts, while acknowledging more work is needed up front.