Los Angeles - The United States steamrolled Samoa 27-0 in the Cup final to win the Las Vegas Sevens on Sunday, seizing the World Rugby Sevens Series lead ahead of their semi-final victims New Zealand.

Tied with New Zealand atop the standings coming into the week, the Eagles beat the Kiwis 24-19 in the semi-finals to reach their fifth final in five events so far this season - then finally broke through for a win to launch ecstatic scenes at Sam Boyd Stadium.

"If we were going to win one of them, the one at home is the one we always wanted," said a beaming US captain Madison Hughes.

Ben Pinkelman scored two tries and there were tries from Matai Leuta, Hughes and Maceo Brown along with a stifling defensive performance from the hosts against Samoa, who beat Argentina 33-19 in the other semi-final to reach their first Cup final since Paris in 2016.

It was a closer affair in the semi-finals, as Carlin Isles scored his third try of the match after the siren to give the United States a 24-19 triumph over the All Blacks Sevens.

First-half tries from Sione Molia and Kurt Baker gave New Zealand an early 12-0 lead, but the Americans had pulled ahead 14-12 at the break.

Folau Niua, however, fooled his defenders with a rare race away try up the middle to put the teams on the board and the Americans finished the first half with Isles striking off the breakdown for a converted try.

Another Isles try stretched the lead before a try from Kiwi captain Tim Mikkelson knotted the score at 19-19. But Isles came through again to give the United States a chance to defend their Vegas title.

"We went down 12-0 real quick and that's tough to play yourself out of against a team like that," said the United States' Ben Pinkelman of a New Zealand team that beat the Americans in the finals at Dubai and Sydney. "We had to play pretty scrappy. It wasn't wide open for us but we stuck to our plan and we were able to get the job done."

The United States is now top the standings at the halfway stage with 98 points.

New Zealand - who had come through pool play unbeaten and downed Fiji in the quarter-finals - kept it close at the top of the standings with a victory over Argentina in the third-place playoff.

New Zealand scored three late tries to beat the South Americans and are five back on 93 points heading into next weekend's Vancouver Sevens.

Earlier, the Blitzboks lost their fifth-place semi-final 14-12 to Fiji.

MATCH CENTRE: Las Vegas Sevens

Standings after five rounds: 

1. USA 98 points, 2. New Zealand 93, 3. Fiji 84, 4. England 68, 5. South Africa 67, 6. Australia 57, 7. Samoa 49, 8. Argentina 46, 9. Scotland 42, 10. Spain 39