His comments, at a news conference in Lisbon, came as Portugal's president, Marcelo Rebelo de Sousa, hailed the Security Council's choice of Guterres for the top UN job as a "historic moment" for the country.

Guterres, who also served as UN High Commissioner for Refugees for 10 years until last December, acknowledged in his first public statement after being chosen unanimously and by acclamation as the Security Council's recommendation for secretary-general, that "enormous challenges" await him if he is confirmed in the post by the UN General Assembly.

Speaking at the Ministry of Foreign Affairs in Lisbon, he promised to “serve the most vulnerable, the victims of conflicts, of terrorism, of rights violations, of poverty, of injustices."

He noted that so far he had only been "recommended" by the Security Council, and that the current incumbent, Ban Ki-moon, remains in the post until the end of this year.

Flanked by Portugal's foreign minister, Augusto Santos Silva, who had overseen what Guterres himself called an "extremely effective campaign" by the country's diplomats in his favour, the former prime minister expressed his “profound recognition” of this work.

“Humility” and “gratitude” had been Guterres's first words to describe what he felt at the Security Council's decision.

He praised the “exemplary process of transparency and of openness” of the unprecedented selection procedure, which for the first time included open hustings at which candidates were quizzed by journalists and citizens of various countries.

Speaking in turn in four languages - Portuguese, English, French and Spanish – Guterres said that he hoped that the process “represents an increased capacity for, in unity and in consensus, having the possibility of taking in time the decisions that the turbulent world in which we live demands."

Elsewhere, Portugal's president, Marcelo Rebelo de Sousa, said of the choice of Guterres as secretary-general, that he had three words: "the first of praise, the second of hope and the third of pride."

Addressing journalists during a visit to a sailing ship in Lisbon, de Sousa described the development as "a historic moment for Portugal" and said that the UN now had "a unique opportunity to rethink, review, reform [itself] in the service of the international community".