Guterres, a former head of UN Refugee Agency UNHCR and Portuguese premier, was due to be nominated later in the day by the UN Security Council.
“I know Guterres very well and consider him a superb choice,” Ban said after talks in Rome with Italian President Sergio Mattarella.
The new UN chief has “deep compassion,” ability to work “around the clock,” a “wide knowledge of world affairs” and a “lively intellect,” Ban said.
The outgoing secretary-general looked back at his record and at the looming entry into force of the Paris Climate Agreement. “Climate change has been my top priority throughout my 10 years in office,” he said.
Ban listed strengthening peace operations, achieving sustainable development, upholding human rights and easing humanitarian suffering as challenges for Guterres, whose nomination dashes hopes of the UN picking its first-ever female leader.
“As the ninth man to serve as secretary general, Guterres has a special responsibility to include, support and empower the world’s women and girls,” said Ban.