The US, Fiji, and New Zealand have qualified for the Tokyo Olympics in rugby sevens after making the London Sevens quarter-finals.

The top four from the ongoing sevens world series automatically qualify, and the leading three are guaranteed their berths.

Australia have also made the quarter-finals at Twickenham despite narrowly losing to the US in their final group match.

The US, the only team to reach at least the semi-finals at every series this year, knocked off Spain and Wales but was under pressure from Australia.

When American Steve Tomasin was sin-binned, Australia pounced to lead 17-12.

But Tomasin came back to score a try from his own half, and Madison Hughes made the conversion for the US to win 19-17 and stay unbeaten.

South Africa, fourth in the series standings, have almost locked up the fourth Olympic qualifying spot after winning their pool and seeing nearest rivals England fail to reach the quarter-finals.

On Sunday, the quarter-finals are: United States versus Canada, Fiji versus Ireland, South Africa versus Australia and New Zealand versus France.

South Africa were the most impressive in pool play, going unbeaten in putting 49 points on Japan, 45 on Canada, and 40 on Argentina.

Fiji, the Olympic champion, was made to fret by only Samoa, which led 17-14 until Fiji newcomer Asaeli Tuivuaka scored the go-ahead try and Waisea Nacuqu got the insurance try in injury time for 26-17.

England were in trouble from the first game, which they lost to Ireland 21-17.

The English came back in a thrilling second half to lead 17-14 with time almost up, but Irish replacement Mike McGrath, on debut, raced through to score.

In the meantime, New Zealand comfortably beat Scotland and Ireland, and left England needing to beat the Kiwis by 10 to reach the quarter-finals.

England led 17-7 until a Tone Ng Shiu try limited its bittersweet win to 17-12.