Michiko Tsukamoto, who was just 10 years old when an atomic bomb was dropped over her hometown of Hiroshima in 1945, on Tuesday urged countries that have not signed a landmark nuclear weapons ban treaty to do so quickly.

"Last year the nuclear ban treaty was made. I felt years and years of (the) hibakusha's work bore fruit and we are one step closer to achieving our dream of a nuclear-free world," she said at a U.N. headquarters event.

The treaty, which was adopted in July last year by 122 countries, will come into force after 50 countries sign and ratify it. So far 69 countries have signed it and 19 ratified it.