Tokyo, Japan - Team USA crushed Australia 79-55 on Wednesday to maintain its long unbeaten streak in women's Olympic basketball and set up a last four meeting with Serbia at the Tokyo Games.

Breanna Stewart top scored with 23 points, including two of three from the three-point line, for the heavily favored US team, who dominated the first quarter 26-12 and never looked back.

The US have won eight of nine Olympic golds available since 1984 and are unbeaten at the Games since the last of their three losses came in 1992.

Australia did beat the US in a tune-up but were a different proposition without star player Liz Cambage, who is sitting out the Games for mental health reasons.

"It's totally different," Sue Bird said. "When you have players like Elizabeth Cambage, the presence, the focal point that she is, the focus we have to put on her ... the scout reports change, everything is different."

On Friday they have a semi-final date with Serbia, who progressed 77-70 over China led by the 18 points of Jelena Brooks.

"I've played with a bunch of them, so I know first-hand – I've competed against a lot of them, so I know first-hand when they step on the court, they're just out there to play basketball and to have fun, and they're good at it," Bird added.

"So that's what we're going to be facing. It's not going to be easy."

Hosts Japan in contrast won an absolute thriller with Belgium 86-85, thanks to Rui Machida's three-pointer 16 seconds from time, to set up a semi with Spain or France.

Belgium led by seven going into the final quarter but stayed in touch and levelled with just under five minutes to play.

The teams were nip and tuck in the final stages and Belgium led by two from Julie Allemand's pair of free throws with 37 seconds to go.

Machida swung things back in favor of Japan and they reached the last four when Belgium's Kim Mestdagh took responsibility for the final shot, only for the ball to rattle off the bucket and stay out.