2021-07-30 06:31:12 GMT2021-07-30 14:31:12(Beijing Time) Xinhua English UN Secretary-General Antonio Guterres attends the UN food systems pre-summit via video link on July 26, 2021. The United Nations on Wednesday wrapped up a three-day pre-summit on the world's food systems, casting light on the world's greatest food-related challenges and setting the table for September's ambitious full summit at UN headquarters in New York. (Giuseppe Carotenuto/FAO/Handout via Xinhua) ROME, July 28 (Xinhua) -- The United Nations on Wednesday wrapped up a three-day pre-summit on the world's food systems, casting light on the world's greatest food-related challenges and setting the table for September's ambitious full summit at UN headquarters in New York.