Human shield army hits 10,000.
The Human Shield Movement says Steven Morris joins supporters from 22 countries who have pledged to go on the mission.
They are ready to travel to Iran and position themselves around civilian sites and infrastructure in a bid to prevent an attack.
Steven, of Birmingham, said: "If we start bombing a sovereign nation that offers no direct threat to any nation, the world will be a much more dangerous place."
The Human Shield Movement's David Tyler said: "None of the shields wants to die but all are unwilling to sit by and wait for politicians to launch another disastrous war in their name."
Volunteers of the group travelled to Iraq in 2003 to try to stop military action.