“On the International Day for the Total Elimination of Nuclear Weapons, we reject the claim that nuclear disarmament is some impossible utopian dream.”

That’s how United Nations Secretary-General António Guterres on Monday began his statement marking the ninth annual day dedicated to destroying the weapons of mass destruction.

“Eliminating these devices of death is not only possible, it is necessary,” Guterres stressed. “At a moment of rising geopolitical division, mistrust, and outright aggression, we are in danger of forgetting the terrible lessons of Hiroshima, Nagasaki, and the Cold War, and inciting a humanitarian Armageddon.”

Guterres’ warning came amid heightened fears over a nuclear disaster or warfare related to Russia—which has the world’s largest nuclear stockpile—invading Ukraine, which is backed by NATO nations including the United States, the country with the second-most nuclear weapons.

U.S. President Joe Biden’s national security adviser, Jake Sullivan, said during a Sunday interview on NBC‘s “Meet the Press” that the administration has engaged in high-level talks about Russian President Vladimir Putin’s nuclear threats, including in a speech last week.

“If Russia crosses this line there will be catastrophic consequences for Russia. The United States will respond decisively,” Sullivan said. “Now, in private channels we have spelled out in greater detail exactly what that would mean, but we want to be able to have the credibility of speaking directly to senior leadership in Russia and laying out for them what the consequences would be without getting into a rhetorical tit for tat publicly.”

Responding to Sullivan’s remarks in a series of tweets Monday, the Nobel Prize-winning International Campaign to Abolish Nuclear Weapons (ICAN) emphasized that using such weapons would indeed be catastrophic “for the entire planet.”

“So no, this is not the time to figure out whether one side is ‘bluffing’ or not,” ICAN declared. “This isn’t a card game, the risk of nuclear war is increasing with every threat. Using nuclear weapons or threatening to use nuclear weapons is unacceptable and this must stop now.”

“It’s time for all countries to condemn all threats to use nuclear weapons, and it’s time to eliminate these weapons of mass destruction for good,” the group added. “The nuclear ban treaty is our clearest path to do so.”

Just last week, five more nations signed on to the Treaty on the Prohibition of Nuclear Weapons (TPNW)—which led to ICAN’s Nobel prize—and two more countries ratified the agreement.

Barbados, Burkina Faso, Equatorial Guinea, Haiti, and Sierra Leone brought the treaty’s total signatories to 91 while Congo and the Dominican Republic deposited their instruments of ratification with Guterres to bring the states parties to 68.

“With more and more countries joining the nuclear ban treaty, we are taking significant steps towards the abolition of these weapons,” ICAN executive director Beatrice Fihn said during a ceremony at U.N. headquarters last Thursday. “As the number of countries signing and ratifying the TPNW grows, the pressure on the nine nuclear-armed states and their supporters to join the treaty grows.”

“The strengthening of the treaty is particularly welcome at this time when the war in Ukraine has seen the risk of nuclear weapons use increase, and one of the world’s largest nuclear-armed states has made undisguised threats to use its arsenal with all the devastation that implies,” she added.

Along with commending the countries that “made the courageous choice to sign or ratify this landmark treaty,” Peter Maurer, president of the International Committee of the Red Cross, also put the developments in the context of Russia’s war on Ukraine during a speech at the event.

“At a time when, against the backdrop of the conflict in Ukraine, nuclear deterrence theories seem to be regaining vigor, it is critical to refocus the debate on the human cost of nuclear weapons,” he said. “This is the benchmark against which the moral, ethical, and legal acceptability of a weapon is to be judged, and deterrence theories are to be evaluated.”

In addition to Russia and the United States, the countries known to have nuclear weapons are China, France, India, Israel, North Korea, Pakistan, and the United Kingdom.

While none of those nations have backed the TPNW, some support the Treaty on the Non-Proliferation of Nuclear Weapons (NPT), for which there was a global summit in August.

During that event, the parties to the NPT “came close to consensus on a substantive outcome,” Guterres noted Monday. “While this unique moment failed to result in the outcome we so desperately need, we urge all states to use every avenue of dialogue, diplomacy, and negotiation to ease tensions and reduce risk.

“More broadly, we need a new vision for nuclear disarmament and nonproliferation,” he continued. “My proposed New Agenda for Peace calls for meaningful disarmament and developing a common understanding of the multiple threats before us so we can end the nuclear threat, once and for all.”

“Eliminating nuclear weapons would be the greatest gift we could bestow on future generations,” the U.N. chief concluded. “On this important day, let us commit to forging a new consensus around defusing the nuclear threat for good and achieving our shared goal of peace.”