Transgender weightlifter Laurel Hubbard takes centre stage at the Tokyo Games on Monday and Ethiopia-born Dutch runner Sifan Hassan faces a daunting day on the athletics track in her ambitious pursuit of an Olympic treble.

On day four of the athletics in the sweltering Japanese capital, the 28-year-old Hassan will run in heats in the 1500m in the morning, before again taking to the track in the evening session for the final of the 5,000m.

The two-time world champion will also go in the 10,000m later in the Games, which are now into their final week and hotting up in every sense -- temperatures in Tokyo over the coming week are forecast to range from maximums of 30 to 34 Celsius (up to 94F).

There will also be the women's 100m hurdles final and men's long-jump final Monday, while there are three gold medals up for grabs in gymnastics -- in men's rings, women's floor exercise and men's vault.

Golds are also going begging in badminton, wrestling, shooting, sailing and event jumping.

New Zealand's Laurel Hubbard transitioned to a woman in her 30s
New Zealand's Laurel Hubbard transitioned to a woman in her 30s AFP / ADRIAN DENNIS

Track cycling meanwhile gets under way at these pandemic-delayed Games, with the women's team sprint title the first gold at Izu Velodrome.

But it is weightlifting which will be in the spotlight because of New Zealand's Hubbard.

The 43-year-old, who was born male and competed as a man before transitioning to become a woman, makes her Olympic debut -- the IOC says she is the first openly transgender woman to compete at a Games, hailing it as a landmark moment for the Olympic movement.

However, her historic presence in the women's +87kg category on the elite stage raises complex issues of bioethics, human rights, science, fairness and identity in sport.

"Laurel Hubbard is a woman, is competing under the rules of her federation and we have to pay tribute to her courage and tenacity in competing and qualifying for the Games," IOC medical chief Richard Budgett told reporters in Tokyo.

Sifan Hassan is eyeing a historic Olympic treble in Tokyo
Sifan Hassan is eyeing a historic Olympic treble in Tokyo AFP / Jewel SAMAD

Supporters say her appearance is a victory for inclusion and trans rights.

Critics argue she has an unfair advantage over female rivals due to physical attributes locked into her body during her decades as a male.

While track cycling is just starting in Tokyo, the badminton competition is reaching its climax, with China's reigning Olympic champion Chen Long facing formidable Dane Viktor Axelsen.

"Obviously I want more than just a final -- this is not enough for me," said Axelsen, the world number two.

Another title for Chen would give China a bit more breathing space at the top of the overall medals table, which the Asian country leads from the United States, with hosts Japan third.

Women's football is also near the business end. There is a local derby in the first semi-final as Megan Rapinoe's United States, the reigning world champions, clash with Canada.

In the other last-four showdown, Australia take on Sweden, the losing finalists at the 2016 Rio Olympics.

"We live for these moments," said the American Rose Lavelle after her side needed penalties to squeeze past the Netherlands in the quarter-finals.

"Obviously, there is pressure when you are on this team. But I think pressure is a privilege, and we are ready for these moments."