By Nick Mulvenney

RIO DE JANEIRO (Reuters) - New Zealand and Australia were both given a fright by the United States but remained on course to meet in the inaugural Olympic women's sevens final by reaching the semi-finals unbeaten in Rio on Sunday.

World series champions Australia needed a late converted try to draw 12-12 with the Americans in the pool stage in the afternoon but blanked Spain 24-0 in the evening to set up a meeting on Monday with Canada, who beat France 15-5.

New Zealand had romped into their quarter-final against the Americans but were forced to defend a 5-0 lead with only six players for three minutes of the second half before securing their passage to a semi-final against Britain, 26-7 winners over Fiji.

"Full credit to our girls, to defend our line with six like that was awesome," said New Zealand's Kelly Brazier.

"Defense wins games and we pride ourselves on that. A win's a win, 5-0, 2-0, we'll take it."

After racking up 109 points in their first three matches, New Zealand had been held to just one Portia Woodman try, her sixth of tournament, when American flyer Jessica Javelet was taken down chasing a kick through.

The referee decided against a penalty try but New Zealand's Tyla Nathan-Wong was sent to the sin bin, setting up the dramatic conclusion to the second day's action at the Deodoro Stadium.

Australia's progress was smoother, Charlotte Caslick scored a brace and Emma Tonegato once to both move to six tries for the tournament, but coach Tim Walsh admitted his side had been far from their best.

"Today we grinded out wins which is what good teams need to do," he said.

"In any tournament the quarter-final's always the big one, but now we're playing for a medal. And we're not happy with a bronze or a silver."

The third seeded Canadians, who were stunned 22-0 by Britain in their final pool match earlier on Sunday, recovered from a poor start against a fired-up French side to progress to the last four.

Jade Le Pesq scored the opener for France before the Canadian responded with tries to Kayla Moleschi, Bianca Farella and Ghislaine Landry.

Abbie Brown gave Britain the perfect start to their match against the physical Fijians when she snatched the kickoff out of the air and raced away to score the opening try after 13 seconds.

Litia Naiqato loped over the line with the ball in one hand to level the scores halfway through the first half but Britain responded with tries from Alice Richardson and Joanne Whatmore with Brown crossing again for the only score after the break.

"It is a team thing," Brown said. "I happened to be in the right place at the right time. We stuck to our principles and basics and came out with the win."

Hosts Brazil, Colombia, Kenya and Japan were the teams to miss out on the knockout rounds.

(Editing by Bill Rigby/Greg Stutchbury)