Mr Johnson wants young people to become 2012 athletes or engineers
Urgent work is needed to divert young people away from violence and towards the 2012 Olympics, London's mayor said.
Boris Johnson told a conference that, without help, thousands of teenagers would fall into lives of crime.
"We have a chance of helping some of those kids who might otherwise go wrong in their lives into that Olympic team in 2012," the mayor said.
Twenty-seven teenagers have died violently in London this year, already exceeding last year's total of 26.
Mr Johnson discussed violence in the capital with a 400-strong group of crime victims, ex-offenders, community activists and youth workers.
"There are thousands of kids across the city whose lives at the moment could go either way," he said.
Mr Johnson said they should be helped to train towards joining the 2012 team or become one of 20,000 engineers working on the Olympic site in east London.
"I want some of those London kids to be filling those jobs and I want kids that are at risk of going wrong to be among those engineers."
Mr Johnson promised "hard-hitting new plans" as part of a youth violence strategy to be announced in November.
The annual Gangs, Guns and Weapons Practitioners Forum event in Wembley, north-west London, was organised by the mayor's office.
The conference works in conjunction with the Metropolitan Police Service, London Probation Service, Home Office and other bodies.
Conference chair Viv Ahmun said: "Some young people growing up in deprived areas feel that they have no future.
"Many are angry and think nothing of hurting other people as they struggle to make sense of their lives. For most gang members, gangs meet a need."
Mr Ahmun added: "When they are more effectively nurtured to meet their needs in a better way, they will decide to stop being a gang member."
Kit Malthouse, deputy mayor for policing, said: "Young people are part of the solution to the problem of youth crime. We need to work together for real long-term change."