The USA suffered deep disappointment on the track at the Tokyo Olympics on Thursday while Australian teen Keegan Palmer flew to a stunning skateboarding gold medal.

The USA men's basketball team beat Australia 97-78 thanks to 23 points from Kevin Durant to reach a fourth consecutive final where they will face France, who stunned the Americans in their opening match.

Spain struck double gold in sports making their Olympics debut. Sandra Sanchez Jaime won the inaugural karate title at the spiritual home of martial arts, the Nippon Budokan, while Alberto Gines Lopez took the first sport climbing honours.

The USA's poor day on the track began with a stunning flop in the men's 4x100 metres relay heats, and extended to red-hot favourite Grant Holloway's defeat to 31-year-old Hansle Parchment in the 110m hurdles.

"I don't think a lot of people expected me to win," said Parchment.

Things did not improve in the evening session when not a single US runner got among the men's 400m medals in a race won by Steven Gardiner of the Bahamas. 

Colombia's Anthony Jose Zambrano took silver in 44.08sec and nine years after he won in London, Grenada's Kirani James won bronze in 44.19sec.

The USA's defending 1500m champion Matthew Centrowitz finished outside the qualifying spots for Saturday's final.

Some American pride was restored by shot putter Ryan Crouser, who hurled an Olympic record 23.30 metres to retain his title, and pole vaulter Katie Nageotte, who cleared 4.90m to win a low-key women's pole vault competition.

Those golds helped the USA cut China's lead at the top of the overall Games medals table to five golds.

'Total embarrassment'

Perhaps the biggest shock for Team USA was their men's relay team, the world champions and pre-Games favourites, who finished a desultory sixth in their heat to miss out on the final.

Sprint legend Carl Lewis called it a "total embarrassment" as Trayvon Bromell, Fred Kerley, Ronnie Baker and Cravon Gillespie became the first US quartet to fail to make the final from a completed heat.

"We just didn't get the job done today," said Kerley. "No excuses."

Portuguese triple jumper Pedro Pichardo leapt 17.98m — the seventh longest in history — to win gold and veteran decathlete Damian Warner of Canada produced two days of consistent excellence to win gold.

In the heptathlon, Belgium's Nafissatou Thiam successfully defended her title, helped by the withdrawal due to injury of British world champion Katarina Johnson-Thompson on the first day.

At the Ariake Urban Sports Park, 18-year-old Palmer wrapped up the Olympics' inaugural skateboarding programme with a brilliant gold medal in the men's park event.

Uncorking a kickflip 540 he had saved for the occasion, the Australian scored a massive 94.04 points in his first run before bettering his score to 95.83, way ahead of silver medallist Pedro Barros's 86.14 and American Cory Juneau, who claimed bronze with 84.13.

USA beat Boomers

In basketball, Durant scored 23 points and Devin Booker added 20 as the USA stormed back to beat Australia after trailing by three points at half-time.

The defending champions will go head-to-head with France who booked their place in the final with a nail-biting 90-89 win against Luka Doncic's Slovenia.

America's Nelly Korda took control of the women's golf when she fired a nine-under 62 in round two — after coming close to carding only the second 59 in women's professional golf.

Korda, needing a birdie on the last hole for a magical 59, took double-bogey but she still has a four-shot cushion at halfway at par-71 Kasumigaseki Country Club.

Quan Hongchan, 14 and the youngest member of China's team, produced three maximum scores to win the women's 10m platform and secure China's sixth gold medal out seven diving events so far.

And India, a one-time hockey superpower, celebrated their first medal in the sport in 41 years when their men's team beat Germany 5-4 to win bronze.

The men's 20-kilometre walk was moved to Sapporo in a bid to avoid Tokyo's punishing summer heat, but it was 32 degrees Celsius during the afternoon race. Italy's Massimo Santo conquered the conditions to win.

In what is expected to be her last Olympics, 36-year-old Megan Rapinoe signed off with two goals and a bronze medal as the United States beat Australia 4-3 in the women's football play-off.