The world number 21 produced a storming display to upset the rest of the field in the 2028 Olympic and Paralympic Games host city.

Lee finished 22 points clear of nearest challenger Bruce Demeter of Hungary, who topped the qualification standings, with a total of 1,468 at the Fairplex events complex in Pomona in Los Angeles County.

Demeter could not live with the South Korean across the competition, ending with an overall score of 1,446.

His compatriot Balázs Szép came through to take the bronze medal, one point adrift of his team-mate.

Reigning world champion Jung Jinghwa of South Korea endured a difficult outing as he finished 22nd, while Olympic gold medallist Alexander Lesun of Russian was 13th.

"Today everything was good: laser-run, fencing, swimming and riding,” the victorious Lee said. 

“For the South Korean team it was a great day, with Jun Woongtae also finishing in fifth.

“This is an important year for us with the Asian Games in Jakarta as well as all the UIPM competitions and we are very happy to perform well here in Los Angeles where the conditions have been perfect.”

UIPM President Klaus Schormann claimed men’s final provided "one of the most exciting finishes we have seen in many years".

"That drama shows that the athletes will always give their all," he added. 

"It was a very exciting moment today."

The mixed relay will bring the event in Los Angeles to a close tomorrow.