Four teams remain in contention for the USA Sevens title after a second enthralling day of action in Las Vegas on Saturday.
After a second pulsating day in front of 35,716 fans, USA beat Kenya to set up a semi-final with defending champions Fiji on day three, while South Africa await Australia after beating New Zealand for the first time since the 2014 Port Elizabeth Sevens.
In the first quarter final Mike Friday's hosts beat his former side Kenya 26-14 to delight of the home crowd and booked their place in the last four of the fifth round on the World Rugby Sevens Series thanks to tries from Danny Barrett, Perry Baker, Martin Iosefo and Zack Test.
"I think the first three games we weren't playing up to our potential and let ourselves down a little bit," said captain Madison Hughes.
"I think the fight and attitude from the boys in the quarter final showed our tue character.
"Kenya are a quality side who beat New Zealand earlier in the day, we knew we had to be at our best to beat them and the attitude from the team was excellent to get the job done."
Kenya had earlier beaten New Zealand 22-0, their first win over the All Blacks Sevens side since the 2013 Wellington Sevens, to top Pool A before coming up short against the USA despite Collins Injera scoring his fourth try of the weekend and 218th overall.
Ben Ryan's Fiji bounced back from their opening pool match defeat to Samoa to top Pool C thanks to a narrow 15-12 win over Argentina before beating Japan 36-7 in the quarter finals. Two tries from Jasa Veremalua and one each for captain Osea Kolinisau, Jerry Tuwai, Pio Tuwai, Savenaca Rawaca and Amenoni Nasilasila proved the difference to set up a semi final with the hosts.
The Blitzboks will meet Australia in the second semi final after Seabelo Senatla scored his eighth and ninth tries of the tournament to help his side beat the Wellington and Sydney champions New Zealand 14-7. It was Neil Powell's first win over Sir Gordon Tietjens since the 2014 Port Elizabeth Sevens, ending a run of five successive defeats.
In the fourth and final quarter final tries from Ed Jenkins, Allan Fa'alava'au and two from Sam Myers gave the Sydney Sevens runners-up to a 26-12 win over Los Pumas.
Day Three fixtures:
United States v Fiji
South Africa v Australia
Day Two results:
Portugal 0-31 Russia
New Zealand 0-22 Kenya
Samoa 17-31 France
Fiji 15-12 Argentina
Scotland 19-26 Japan
Australia 36-7 England
Canada 10-17 Wales
South Africa 29-0 USA
Kenya 14-26 USA
Fiji 43-7 Japan
South Africa 14-7 New Zealand
Australia 26-12 Argentina
Scotland 17-12 Samoa
France 21- 19 England
Wales 31-12 Portugal
Russia 19-10 Canada
With thanks to World Rugby's official website