United Kingdom, June 3 -- Heidi Klum feels "honoured" to have become UNICEF USA's newest ambassador.

The 53-year-old model first began working with the children's charity in 2011, and Heidi is thrilled to have been named an ambassador for the organisation.

Heidi told People: "I'm incredibly honoured by this recognition.

"After working closely with UNICEF for a while now, becoming a UNICEF USA Ambassador means so much to me because it deepens my commitment to helping children around the world. It's a privilege to use my voice to support UNICEF's mission and advocate for every child's right to a healthy, safe, and hopeful future."

Heidi - who has Leni, 22, Henry, 20, Johan, 19, and Lou, 16 - admitted that some of her past trips with UNI...