New Zealand, USA, Samoa and Argentina all progressed through to the Cup semi-finals of the HSBC USA Sevens after another enthralling day of action at the Sam Boyd Stadium. 

With the tournament taking place over three days, this middle day was a combination of the conclusion of the pool stage and the first of the knockout matches as the Challenge Trophy quarter-finals and Cup quarter-finals finished day two. 

The HSBC USA Sevens is the fifth tournament on the HSBC World Rugby Sevens Series 2019. This stop marks the halfway point on the World Series meaning that every point is vital, not only for the title race, but also in the chase for qualification for the Tokyo 2020 Olympic Games - the top four teams at the end of the series will gain automatic qualification.

Samoa are heading to their first Cup semi-final since 2016 and after captain David Afamasaga praised their belief and performance. 

"We had the self-belief that we could do it and it just showed out there in that last game," said Afamasaga. "Credit to Australia, they gave us a real good battle and that's what rugby is all about, fighting to the end. We definitely are looking forward to tomorrow. We're going to give it our all like we did today." 

The fiercely contested Cup quarter-finals give fans a stellar semi-final line-up on Sunday as the joint leaders on the World Series - New Zealand and USA - will face each other while Samoa and Argentina will meet in the second contest. The matches get underway at 1:12pm local time (GMT-8) with the Cup final taking place at 4:30pm. 

Fiji, South Africa, Australia and England will all compete in the fifth-place semi-finals from 12:28pm local time (GMT-8). 

In the Challenge Trophy, invitational side Chile, Spain, Kenya and Scotland all progressed into the semi-finals after wins over France, Wales, Japan and Canada. Los Leones and Kenya will contest the the first Trophy semi-final while Scotland will clash with Chile in the second. In the battle for 13th place, Wales will open proceedings against Japan on Sunday at 11:00am local time (GMT-8), followed by Canada versus France.

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CUP QUARTER-FINALS

As was the case 12 months ago, New Zealand and Fiji opened the Cup quarter-finals after the former progressed out of Pool A unbeaten and Fiji finished second to Australia in Pool D. The World Series meetings between these two teams have become legendary and this one, the 100th, certainly lived up to that billing. The All Blacks Sevens punished early ill-discipline from Fiji - three penalties finished with Sione Molia crossing after a quick-tap. Fiji stayed calm and Jerry Tuwai flew off the back of a ruck to strike back. Vilimoni Botitu's conversion created their 7-5 lead at half-time. The final seven minutes started with Tuwai and Molia both adding second tries before Kurt Baker put New Zealand 19-14 ahead. As the final minute arrived Fiji had the ball in their possession, dangerously keeping it alive and working with a penalty advantage, however Clark Laidlaw's side showed their durability and prowess at the breakdown to ride out the moments and secure a match-winning penalty.

Next to try and book a place in the last-four were the defending World Series champions and the defending HSBC USA Sevens champions - South Africa and the USA. The Blitzboks started the second day by shrugging off their slow first day, they powered past England in their final Pool C match and looked a completely different side to the one that drew 5-5 with Chile. Mike Friday's outfit also concluded their pool campaign with a victory, prevailing 19-10 over France, and were roared on by an enthusiastic crowd at the Sam Boyd Stadium. Danny Barrett set the USA's tone by taking on four South African defenders and managing to power over the line. Stephen Tomasin and Martin Iosefo then showed their pace out wide to help put the home side 19 points up after seven minutes. After the break, the Eagles didn't let their foot off the gas. Carlin Isles struck off the back of a ruck before Matai Leuta plucked a restart effortlessly out of the air to add their fifth try. Two late scores ensured that the Blitzboks didn't finish the quarter-final without a point but the contest belonged to the hosts as they made history in style with their first ever win over South Africa on home soil. 

The third of four crucial duels saw Australia take on Samoa in a bid to go four from four. Australia's progression out of Pool A saw them finish with their first win over Fiji for three years but they could not follow it up. Tim Walsh's side have never won the title in Las Vegas, their best finish was a runners-up spot in 2016, and had to try to face the knockout stage (and the rest of the tournament) without captain Lewis Hollanddue to him being suspended for a dangerous tackle against Fiji. Australia scored first in their Cup quarter-final but two quick responses from Samoa handed Sir Gordon Tietjens' men a 14-5 lead heading towards the pause. The experienced Australians kept working and Liam McNamara's step made sure that they went into the interval just four points down. The second seven minutes saw the lead constantly change hands and the result was a single-point game at 21-20 in Samoa's favour with 11 seconds to play. John Porch had missed a match-winning conversion attempt in the final moments and on Australia's last throw of the dice he was the man rocked into touch by Melani Matavao. The result was Samoa's first win over their opponents since facing them in Paris back in 2017 and a first Cup semi-final place in three years. 

In the last quarter-final Argentina and England met. With England being the designated team for Great Britain in regard to Tokyo 2020 qualification, the pressure remains strongly on their shoulders and they conceded first as Santiago Mare fended off the attentions of Charlton Kerr. England levelled the match up at seven apiece through Phil Burgess before they had two men sent to the sin-bin - Will Muir and Richard de Carpentier - and the second dismissal had a penalty try added onto it. At the start of the second half, with a 14-7 lead and a two-man advantage, Argentina didn't capitalise as they could have and instead England played sensibly until they were back to six and then seven. Despite having a full compliment of defenders Fernando Luna still found a textbook direct line to cross and the conversion created a 21-7 lead. England weren't done and instead struck back twice through Ryan Olowofela and Tom Bowen. Tom Mitchell's conversion locked the match up at 21-21 and forced a golden point situation. The kick-off belonged to England but they gave away a penalty off it and Los Pumas Sevens patiently worked their way upfield. The match then went full circle as Los Pumas Sevens' opening try-scorer, Mare, became their last. His try duly booked their first Cup semi-final place since the HSBC USA Sevens last year.