Samoa were among the four teams that progressed through to the Cup semi-finals of the World Rugby Sevens Series event in Las Vegas on the second day of action ©World Rugby

Argentina, New Zealand, Samoa and hosts United States all progressed through to the Cup semi-finals of the World Rugby Sevens Series event in Las Vegas on the second 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 knock-out matches as the Challenge Trophy quarter-finals and Cup quarter-finals were held. 

The fiercely contested Cup quarter-finals give fans a stellar semi-final line-up tomorrow as the joint leaders on the World Series - New Zealand and the US - will face each other while Samoa and Argentina will meet in the second contest.

New Zealand sealed top spot in Pool A with a 19-7 win over Spain before beating Pool D runners-up Fiji 19-14 in the quarter-finals.

Their last-four opponents, the US, started today by defeating France 19-10 to finish second in Pool B and then overcame Pool C winners South Africa 29-10 in the last eight.

Despite losing 24-19 to Kenya, Argentina topped Pool B to set up a quarter-final clash with Pool C runners-up England that they won 26-21.

Standing between the South Americans and a place in the final are Samoa, who clinched second spot in Pool A with a 26-19 victory over Canada prior to edging Pool D winners Australia 21-20 in the first knock-out round.

Samoa are heading to their first Cup semi-final since 2016.

"We had the self-belief that we could do it and it just showed out there in that last game," captain David Afamasaga said.

"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 fifth-place semi-finals will see Fiji face South Africa and Australia meet England. 

In the Challenge Trophy, invitational side Chile were among the four teams to progress into the semi-finals after a 17-12 win over France.

They will next go up against Scotland, 21-19 victors at the expense of Canada.

The other penultimate-round match pits Spain against Kenya.

Spain beat Wales 19-7, while Kenya defeated Japan 28-15.

In the battle for 13th place, Wales will open proceedings against Japan before Canada do battle with France.

The event in Las Vegas is the fifth tournament on the 2019 World Rugby Sevens Series tour.

This stop marks the halfway point, meaning that every point is vital, not only for the title race, but also in the race for qualification for the Tokyo 2020 Olympic Games.

The top four teams at the end of the World Series will gain automatic qualification.

New Zealand and the US are currently tied for first place with 76 points each.

Fiji are third on 72 points with South Africa completing the top four on 57.

Events have already been held this year in Dubai, Cape Town, Hamilton and Sydney.