A former UN secretary general has called for an overhaul of the United Nations to better confront global challenges as “some powerful nations” seek to undermine the institution. Ban Ki-moon, who was secretary general of the United Nations from 2007 to 2016, said in Hong Kong on Tuesday that the conflicts in Ukraine and Gaza showed the need for a multilateral response. “The illegal Russian war against Ukraine and the horrific war in Gaza represent one of the most dangerous moments for global security, and challenges to multilateralism, in decades,” Ban told the Fullerton Forum hosted by the University of Hong Kong’s Centre on Contemporary China and the World (CCCW). Ban said that various global crises, including these conflicts, pandemics and climate change, “have shown how we are all interconnected”. “They also make it clear that we need multilateral responses,” he added, according to the speech published by the CCCW. In his speech, Ban thanked China for its role in implementing the Paris Climate Agreement and for its efforts to combat climate change. Ban, who is now deputy chair of The Elders, a human rights group composed of international statesmen founded by late South African president Nelson Mandela, took direct aim at US President Donald Trump, saying the shift towards unilateralism had been “bolstered by the advent of Trumpism” in the United States. He also said the UN mechanism was “being undermined by some powerful nations”, though he did not name the countries. Ban’s speech was delivered against the backdrop of intense air strikes between Israeli and Iranian forces. War broke out between the two countries on June 13, with Israel targeting Iranian nuclear facilities, military bases, senior commanders and nuclear scientists. Amid growing scepticism about the UN’s ability to deal with such crises, Ban said the UN and its agencies should be strengthened “through timely and necessary reforms”. He also said the UN should work more closely with governments, the private sector, civil society, academia, and young people to implement the United Nations Sustainable Development Goals and the Paris Agreement. According to the CCCW website, the more than 70 guests at the forum included foreign consuls general and representatives of international organisations. Ban also emphasised the importance of international cooperation in addressing climate change, criticising Trump’s withdrawal from the Paris Agreement as “seriously impacting global development”. Shortly after being sworn in for his second term as US president earlier this year, Trump announced that Washington would withdraw from the World Health Organisation, the Paris Climate Agreement, the UN Human Rights Council, the UN Relief and Works Agency for Palestine Refugees and the International Criminal Court.