The Invictus Games for injured servicemen and women are to open in the city of Orlando Florida.
The event has the backing of Britain’s Prince Harry and follows the inaugural games in London in 2014.
During the five-day tournament more than 500 athletes from 14 countries will compete in a range of sports.
They include athletics, cycling, tennis and basketball. The main guests at the opening ceremony will be Prince Harry and the US first lady Michelle Obama.
The opening ceremony is also being attended by Hollywood star Morgan Freeman, British singer James Blunt and soprano Laura Wright.
The five-day tournament will see more than 500 athletes from 15 countries compete in a Paralympic-style event that will feature a range of indoor and outdoor sports.
Prince Harry is patron of the Invictus Games Foundation, which oversees the delivery of the event and its legacy.
He said ahead of the opening that he hoped the Games would “smash the stigma” surrounding military mental health issues in the same way the London event had helped people come to terms with physical wounds.
“I’ve spoken to everybody who has severe Post-Traumatic Stress Disorder to minor depression, anxiety – whatever it might be,” he said.
“Everybody says the same thing, if you can deal with it soon enough and have the ability and the platform to speak about it openly, then you can fix these problems.
“And if you can’t fix it, you can at least find coping mechanisms – that’s what it’s all about, there’s no reason people should be hiding in shame after they’ve served their country.”
In an interview with the BBC the prince described the Games as a popular cause to benefit “people who had put their lives on the line”.
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