Presented with this damning assessment, Guterres admitted his organisation was struggling to make members abide by the international laws laid out in the UN Charter.

The UN was "extremely engaged" in solving major global conflicts, he insisted. "But the UN has no leverage - the big powers have stronger leverage.

He questioned whether that extra leverage was being used to produce real and enduring solutions to those conflicts, or just quick fixes. "There is a big difference between the two things," he noted.

Guterres also said his organisation needed reform to tackle "dramatic problems and challenges" facing its 193 members.

"There are those that believe the power of law should be replaced by the law of power," the UN chief said.

"Indeed, when one sees the present policy of the United States, there is a clear conviction that multilateral solutions are not relevant and that what matters is the exercise of the power and the influence of the United States and sometimes in this respect by the norms of international law".

He suggested the UN Security Council - designed to maintain international peace and security - no longer represented the world and was "ineffective".

Any one of the council's permanent members - France, China, Russia, the UK or US - can currently veto resolutions. Both Russia and the US have used this power to frustrate global efforts to end the wars in Ukraine and Gaza.

Guterres claimed vetoes were being used to further individual members' interests, and criticised the fact that "three European countries" were permanent members.

He called for changes to the council's composition - to "regain legitimacy" and "give voice to the whole world" - and to limit veto powers to avoid unacceptable "blockages".