The annual meeting has been chaotic, with Indigenous protesters blocking its entrance last week and negotiations disrupted by a fire inside the venue on Thursday.
Natural disasters have left 279 people dead or missing in Vietnam and caused more than $2 billion in damage between January and October, according to the national statistics office.
South African President Cyril Ramaphosa opened a G20 summit in Johannesburg on Saturday by emphasising the need for "multilateralism" to confront "the threats facing humanity today".