The U2 frontman and activist delivered the sobering assessment to several hundred UN diplomats and staff at an event on Sunday launching Ireland's candidacy for a UN Security Council seat in 2021-22.

While not explicitly saying which countries were responsible, Bono's words appeared to be aimed at US President Donald Trump, who has criticised the EU, NATO, left the Paris climate deal and issued veiled threats to the World Trade Organization over US tariffs.

"I love that it exists, and I'll tell you, I don't take for granted that it exists," Bono said, referring to the United Nations.

"... let's be honest, we live in a time when institutions as vital to human progress as the United Nations are under attack.

"And not just these institutions but what they stand for - an international order based on shared values and shared rules, an international order that is facing the greatest test in its 70-year history."

As part of Ireland's push for the council seat, the Irish government invited ambassadors from the 192 other UN member nations to attend Bono's concert at Madison Square Garden.

Bono, who is also a human rights and humanitarian activist and philanthropist, joked that it's "unusual having a load of ambassadors jumping up and down at a rock and roll show".

"At least you weren't shouting at each other, so that was good."

Ireland is expected to be in a three-way race against Canada and Norway for two seats reserved for Western nations on the Security Council. Elections to fill the seats for a two-year term will be held in June 2020.

Australian Associated Press