TORONTO - Prince Harry launched the official countdown to the 2017 Invictus Games on Monday, promising that the Toronto edition of the Olympic-style sporting event honouring wounded, injured and sick troops would be its biggest yet.

About 600 participants from 16 nations are expected to compete in the event, which is the 31-year-old royal's brainchild.

"This city will become the focal point for hundreds of men and women who use the pull of Invictus glory to motivate their recovery from physical and mental injuries," Harry told a gathering of servicemen at Toronto's Fairmont Royal York Hotel.

"And Toronto will take on responsibility for a competition that has the power to inspire millions of people around the world and to remind us all of the amazing contribution that our servicemen, women and veterans make."

Harry said the desire to found the games took root in 2008 while he was serving as an officer in Afghanistan.

He was forced to leave the front lines after his presence in the war-torn region was leaked to the media, potentially endangering the soldiers serving alongside him, he said.

As he was flying home, burdened by a sense of guilt for abandoning his fellow troops, Harry said he had an experience that reminded him that battles were not always confined to the war zone.

"Once in the air, I stuck my head through the curtain to see three British soldiers, really young lads, younger than me at the time, laid out on stretchers in induced comas. All three wrapped in plastic, missing limbs, with tubes coming out of them everywhere," he said.

"This visceral image was something I'd never prepared myself for and only heard of. It struck me that this flight was just one of many carrying home men and women whose lives would be changed forever."

Harry said sport is a valuable outlet for soldiers trying to recover from their injuries. Smaller competitions playing out in front of meagre audiences inspired him to create a global platform for troops to showcase their athletic accomplishments, and for spectators to be inspired by their achievements, he said.

Harry was also joined at the event by a number of dignitaries including Ontario Premier Kathleen Wynne and Prime Minister Justin Trudeau.

Showing a picture of his grandfather who served during the Second World War, Trudeau said Canada was committed to honouring soldiers during their time on and off the battlefield.

"These individuals, as the name Invictus suggests, are unconquerable," he said. "And this event shines a spotlight on their unwavering strength of character."

Later in the day, Prince Harry and Trudeau traded their formal suits into more relaxed attire when they attended a sledge hockey exhibition game at Ryerson University's Mattamy Athletic Centre. While there, the royal explained why the sport will be part of the games for the first time next year.

"This is Canada, everything happens on ice, doesn't it?" Harry quipped, drawing laughter and applause from the crowd.

Harry also explained that the Games provide role models for those who observe them.

"You young guys, the next generation, these are the perfect people for you to look up to," he said to the audience of youngsters. "It's individuals who have put their life on the line and given service for their country, for their family for their friends."

Trudeau agreed, saying the games give members of the forces a rare chance to step into the public eye.

"To get a chance to have men and women who have served in the forces step out and compete and show their courage and determination and strength, and to be cheered on with family members and friends and all of Canada in the stands, is a wonderful way for us to say thank you," he said.

Harry stood behind the bench with Trudeau and Toronto Mayor John Tory cheering on the athletes during a scrimmage. He also posed for selfies with the players, and greeted onlookers behind the glass.

Capt. Simon Mailloux, who lost his leg in an improvised explosive device explosion in Kandahar in 2007, said he felt a kinship with Harry as a fellow veteran.

"He was in Helmand (province) when I was in Kandahar. He's been in the mud... so he knows us," said Mailloux, who's suiting up for this year's event slated for May 8-12 in Orlando, Fla.

"There's a connection when we talk to him. (He's) probably the perfect spokesperson for us."

Later on Monday, the prince had a private meeting with Ontario Lt.-Gov. Elizabeth Dowdeswell.

Dylan Atack, 26, Hamilton, was waiting outside Dowdeswell's office hoping to get a glimpse of the royal.

"I wanted to make it because I got to meet Her Majesty back in 2010 when she was here. Same spot, so hopefully I'll get lucky again," he said while holding a "Prince Harry Welcome Eh" sign.

The inaugural Invictus Games were held in London in 2014. The Toronto Games, which will take place between Sept. 26-30, 2017, will be the first to feature a national torch relay across all 32 Canadian military bases and neighbouring communities.

The event will help commemorate Canada's 150th anniversary as well as significant military milestones such as the battle of Vimy Ridge and the battle of Dieppe.