The UIPM and World Obstacle revealed details of an alliance in May, following the decision at last year's UIPM Congress to approve obstacle as a replacement for riding as modern pentathlon's fifth discipline.

This partnership featured a collaboration between the two governing bodies on two events, with the North American leg of the Ninja World Cup in the United States the first of those.

Most of the athletes competing at the Orange County Convention Centre are American.

Ninety-three of those are competing in the elite competition, due to be staged tomorrow.

Olivia Vivian of Australia, the Philippines' 100 metres world record holder Precious Cabuya and her compatriot Mark Julius Rodelas are among the other stars who have entered.

A 100m head-to-head sprint format is set to be used for the competition based on the Ninja television broadcast.

World Obstacle President Ian Adamson claimed the "collaboration is a groundbreaking event for the Ninja and obstacle community worldwide as the first international event presenting opportunities for athletes with the Olympic dream".

USA Pentathlon Multisport chairman Tom Shepard and chief executive Rob Stull, who is also a UIPM Executive Board member, added obstacle racing would "provide new interest, new fans and new opportunities for more athletes than ever before" to modern pentathlon.

The move to drop riding and replace it with obstacle discipline has proved divisive in modern pentathlon.

Britain's reigning men's Olympic champion Joe Choong has warned of a mass exile from the sport after the Paris 2024 Olympics, which is set to be the last featuring the equestrian discipline in modern pentathlon.

UIPM Athletes' Committee member Jamie Cooke of Britain told the PA news agency the changes aimed to "safeguard the sport", and said Choong "would be an unbelievable athlete at this".

Opposition has been spearheaded by the Pentathlon United pressure group, which argues the UIPM has neglected the riding element of the sport and called for the UIPM leadership including long-serving President Klaus Schormann to resign.

Modern pentathlon remains off the initial programme for Los Angeles 2028 with a final decision expected at this year's International Olympic Committee session, and Pentathlon United fears "the Executive Board has lost our Olympic place".

The UIPM has argued the addition of obstacle can attract a new fanbase, tap into a mass participation base in obstacle and will make the sport more accessible.

Critics have disputed the suggestion obstacle could lead to an influx of athletes and insist competitors are leaving modern pentathlon.

The Ninja World Cup in Orlando also features age group competition from Thursday (July 27) until Sunday (July 30), and September's World Obstacle UIPM 2023 OCR World Championships in Genk is set to be the second event co-hosted by the two governing bodies.