Ban spoke at a memorial service at UN headquarters today honoring the 22 staff members who died in Baghdad and thousands of others who gave their lives "serving peace" in past years.
He says the UN has learned from its losses and is changing the way it operates to strengthen security, training and provisions for families of victims.
But Ian Richards, vice president of the UN Staff Management Committee, says the UN is now "a target" and must do much more to take care of its staff and "bring staff deaths to zero.