Story highlights David Beckham: It's more important than ever that we stand up for the protection of children

Too many children are being left behind, despite progress, Beckham writes

David Beckham, the English football star, is a UNICEF goodwill ambassador. The opinions expressed in this commentary are his.

(CNN) I first started working with UNICEF when I was playing football for Manchester United. During a preseason tour with the club to Thailand in 2001, I visited a local child protection center that was providing vital support to children as young as five who'd experienced violence and abuse. Seeing the organization's incredible work firsthand had a great impact on me, especially as my son Brooklyn was just 2 years old at the time, and as a new father I wanted to do what I could to help.

David Beckham

Fifteen years later, I feel extremely proud to still be involved in the work UNICEF does for children and last year I stepped up my commitment by launching 7: The David Beckham UNICEF Fund to help protect children from danger.

When I was asked to become a UNICEF goodwill ambassador in 2005, by then-United Nations Secretary-General Kofi Annan, it was one of the proudest and most memorable moments of my life. UNICEF has done more to help children than any other organization in history and to join the ranks of UNICEF ambassadors such as Danny Kaye and Audrey Hepburn was a huge honor.

During my time in this role, I've seen the lorries delivering aid, met the dedicated staff on the ground and seen how they just won't stop until every child has been vaccinated, has access to education, clean water and life-saving food. Until every child is safe.

I've met children and mothers in Swaziland living with HIV, children living in the aftermath of Typhoon Haiyan in the Philippines, severely malnourished children in Sierra Leone and children who've experienced violence and abuse in Cambodia. I won't ever forget these children, their resilience and determination against all odds.

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