USA frustrations are boiling over now. The ball is not straight at the line-out from the Americans and New Zealand pat each other gleefully on the back. Not sure they did much there though.

USA have another bash at the set-piece and this time it goes safely to the tail with Alycia Washington and they'll look to build.

But Naya Tapper is dispossessed far too easily.

USA can't find their rhythm.

Nicole Heavirland concedes the penalty there as she's pulled for being off her feet. The USA defence are looking slightly tired now.

Kendra Cocksedge steps up and slots an easy three points.

USA just can't get their hands on the ball, it's been all New Zealand since they came back out.

Eight minutes of heroic defence from the Eagles but Portia Woodman eventually found a way through and the Black Ferns are at it again.

USA find a turnover and hack the ball clear, as we have a short pause before the line-out.

Aldora Itunu is down receiving treatment for New Zealand.

A better kick from Cheta Emba at the second time of asking.

A great turnover from Hope Rogers to rip the ball from Aroha Savage.

This is heroic defence from the USA.

Almost, almost.

Kendra Cocksedge puts in a chip kick and Stacey Waaka tries to gather on the left wing but USA full-back Cheta Emba just about shepherds her into touch.

Emba then threads through a clearing kick from the line-out but USA have their backs to the wall here.

Victoria Subritzky-Nafatali puts in a good kick to the corner and wins territory for NZ. A much better kick than her first-half efforts.

New Zealand steal the line-out but that's a knock-on from Selica Winiata. Frustration.

The Black Ferns look slightly rattled here - they breezed through their pool so this is the first real test for Glenn Moore's side.

They're being put off by the USA's line-speed and making uncharacteristic errors.

And that's an immediate unforced error from fly-half Kimber Rozier, who knocks on.

Not the start her side would have wanted and a good first opportunity for the Black Ferns.

Right we're back out in Belfast.

Kendra Cocksedge gets us under way.

40 minutes for one of these teams to make the World Cup final.

Just a reminder (as if you could forget) England are playing France in the second semi-final at 19:45 BST.

So stay with us, we've got live text and radio commentary of that one too over on 5 live Sports Extra.

And if you want to have a chat about the rugby, you can tweet me using #bbcrugby.

This has been a quality game of rugby so far - could we see a first upset of the day?

Meanwhile in the other 5pm kick-off, Canada are beating Wales 26-0 at half-time. No shocks there unfortunately bar an epic second-half comeback.

It looks like Wales are heading for a 7th/8th place play-off against Ireland.

And Canada are on course to play Australia for fifth place.

USA have one last chance to take points before the end of the half but wing Naya Tapper is guilty of looking up and the ball slips through her hands.

An enthralling first 40 minutes, the USA are fighting hard here.

Fiona Hayes
Ex-Ireland prop on BBC Radio 5 live sports extra

The USA had New Zealand under lots of pressure and it's not great to come away from that zone with no points - maybe they should look at taking those kicks at goal in the future.

The referee decides to come back for the penalty for a high tackle from New Zealand prop Aldora Itunu.

USA turn down the three-point option though and run it, but it's immediately stripped by the Black Ferns.

Not to be for the USA after all that effort.

Sara Parsons carries from the line-out to start the move as the ball is chucked out to Kris Thomas on the left wing.

Alev Kelter sees the New Zealand flying defence and makes ground with a dummy run.

USA inching ever closer here. Good control but they need a try before the break.

USA are hammering on the door here in the Black Ferns' 22.

But they're being forced back by the huge NZ wall as fly-half Kimber Rozier gets frustrated and kicks over the top.

It's a test for full-back Selica Winiata who deals with it well and kicks into touch.

USA with the line-out in a good position. Four minutes left in the half.

Back on the field though, New Zealand are continuing to kick to Cheta Emba, who pops up with another fine break to worry the Black Ferns defence.

This one is shaping up to be a battle of the runners.

Here goes Alev Kelter, she straightens and drives her legs to make ground through the centre, but that's sloppy from her team-mate.

The ball is knocked-on by number eight Jordan Gray in the tackle, as she carries the ball far too high.

Portia Woodman, I should add, is a relative novice at the game.

The 26-year-old was playing netball for the Northern Mystics back in 2012 before switching to rugby union.

She only re-joined the Black Ferns in 2016 for the first time since her debut in 2013, having missed the 2014 and 2015 campaigns to focus on sevens.

She's got a rather good pedigree though. Both her father and her uncle are former All Blacks.

Fiona Hayes
Ex-Ireland prop on BBC Radio 5 live sports extra

If you can kill New Zealand's ball and stop it getting out to that backline, and also have a good set-piece, that's half the battle against New Zealand - that's not going to happen to them today I think.