Risk of nuclear warfare at its highest point in decades: UN chief

UN Secretary-General Antonio Guterres has invoked Oscar-winning film "Oppenheimer" as he warned that the world faced the highest risk of nuclear war in decades.

At a Security Council session called by Japan on Monday, Guterres said that the biopic about the morally conflicted father of the atomic bomb "brought the harsh reality of nuclear doomsday to vivid life for millions around the world".

"We meet at a time when geopolitical tensions and mistrust have escalated the risk of nuclear warfare to its highest point in decades," he said.

Russian President Vladimir Putin has made thinly veiled threats to use nuclear weapons as he warns the West against its support for Ukraine, which Moscow invaded more than two years ago.

Guterres said, "Nuclear saber-rattling must stop".

"Threats to use nuclear weapons in any capacity are unacceptable," he said.

Elsewhere in the world, tensions surrounding nuclear-armed North Korea have continued to rise and Iran has been enriching uranium closer to the level needed if it decides to build an atom bomb.

Israel, the Middle East's only nuclear-armed power albeit an undeclared one, has been at war since an October 7 attack by Hamas.

Guterres called on the United States and Russia to resume negotiations, at a standstill since the Ukraine war, on a successor to the New START nuclear arms reduction treaty which expires in early 2026.

He also called for progress on other initiatives including the Treaty on the Prohibition of Nuclear Weapons, which entered into force in 2021 but has little practical effect as no nuclear-weapons states are party to it.

"Investments in the tools of war are outstripping investments in the tools of peace. Arms budgets are growing, while diplomacy and development budgets are shrinking," Guterres said.

Push on fissile treaty

The United States, the only country to have used nuclear weapons in warfare, said it would work on one area with ally Japan, whose cities of Hiroshima and Nagasaki were devastated by atomic weapons in 1945.

The United States as well as France said they would join Japan in a coalition to push through the Fissile Material Cut-off Treaty, which would ban production of pluto nium and highly enriched uranium, the key ingredients in nuclear weapons.

Most nuclear states have already stopped production. Discussions on a treaty have been blocked by Pakistan, which believes it would fall behind rival India and which enjoys diplomatic support from China.

"To forestall a potential arms race, we need to see an end to the production of fissile material for use in nuclear weapons, and continue pursuing negotiations on a Fissile Material Cut-off Treaty," said the US ambassador to the United Nations, Linda Thomas-Greenfield.

Japanese Foreign Minister Yoko Kamikawa, who led the meeting, vowed that Tokyo "will further increase international and political attention" toward the treaty.

Kamikawa also called for work to ensure that nuclear weapons are not placed in space.

The United States said last month that Russia was developing a system to send nuclear weapons to space, an assertion denied by Putin.

"During the Cold War, despite the confrontational environment at that time, the international community established legal frameworks to ensure the peaceful and sustainable use of outer space, which prohibit placing nuclear weapons or any other kinds of weapons of mass destruction in outer space," Kamikawa said.

"Even now, Japan firmly believes that outer space must remain a domain free of nuclear weapons," she said.