Cho (pictured top), a Vancouver 2010 relay bronze medallist who was born in Seoul, South Korea and moved to the United States aged four, said Chun, formerly coach of South Korea, had demanded that he tamper with the skates of Canada's Olivier Jean at the 2011 World Team Championships in Warsaw.

He said he complied after the command was made a third time and in Korean by Chun, who was dismissed as South Korean coach before the Turin 2006 Winter Games and then took over the Canadian team before moving on to the United States.

Chun is currently suspended while US Speedskating carries out an investigation into allegations that he has physically and psychologically abused skaters.

Chun, who faces no criminal charges from police, denies the allegations and is supported by nine skaters.

Jean was unable to compete in the 5,000 metres relay final in Warsaw because the blade of his skate had been bent out of shape and Canada, with only three skaters instead of the full complement of four, finished last.

Chun was said to have been angry with the Canadian tactics in the semi-final, which saw the United States eliminated.

Jae Su Chun is currently suspended for allegedly physically and psychologically abused skaters
"When he [Chun] spoke in Korean, I knew he was serious," said Cho at a news conference.

"The repetitiveness and aggressiveness of how he came at me was very intimidating...I knew he wasn't going to take no for an answer."

Cho, who faces a life ban for what he calls "the biggest mistake of my life", said fellow skater Jeff Simon heard Chun's first request in English.

He added that the tampering had taken a few seconds, and had been done with a blade bender normally used to ensure blades followed the correct line.

Cho said he had apologised to Jean on the phone.

"He sounded personally understanding," Cho said.

"I always knew it was wrong that day.

"I was very scared."

Olivier Jean (L) is said to have accepted an apology from Simon Cho (C)

Ian Moss, chief executive of Speed Skating Canada, said Jean had accepted Cho's apology.

"Simon Cho showed respect and humility today in admitting to his mistake, and Speed Skating Canada appreciates that he has come forward and that he apologised to Olivier in a phone call," Moss said in a statement.

US Speedskating said it was "shocked and disappointed" by Cho's actions, and has apologised to the Canadian team.

The US Speedskating investigation has ruled against claims by 13 short track speed skaters that Chun should be dismissed as coach for abuse they claim included slamming an athlete against a wall, throwing bottles and chairs at skaters and telling women skaters they were fat.

"The investigation has found that the complaints and evidence presented do not constitute physical or emotional abuse or a pattern of abuse," US Speedskating said in a statement.

Contact the writer of this story at [email protected]