By Rebecca Heilweil

On Tuesday, the director of the United Nations' Institute of Disarmament Research, Renata Dwan, said that the risk of nuclear war is at its greatest since the U.S. deployed atomic bombs against Japan.

"The risks of nuclear war are particularly high now, and the risks of the use of nuclear weapons, for some of the factors I pointed out, are higher now than at any time since World War II," [Dwan told reporters] ( in Geneva. A portion of those heightened tensions, she added, can be attributed to competition between the U.S. and China.

But John Borrie, who directs the Institute's research on weapons of mass destruction, cautioned against fear of "general nuclear war."

"We're not looking at the Cuban Missile Crisis of 1962 or the Berlin Airlift of the 1940s," he told Cheddar on Thursday. Rather, he says, we should be concerned about the increasing number of states with nuclear capabilities, and rising tensions between those states, which both increase the likelihood of a nuclear conflict.

There are [now nine countries] ( known to be in possession of nuclear weapons.

Borrie pointed to North Korea's missile launches, rising conflict between India and Pakistan, and tensions between Russia and NATO members. He called on leaders of states with nuclear capabilities to make declarative statements eschewing the possibility of nuclear war, and to be more transparent about their nuclear capabilities.

"At the same time, you have arms control agreements breaking down," said Borrie. The Trump administration has begun the process of withdrawing the United States from the Intermediate-Range Nuclear Forces Treaty, an arms treaty with Russia that was signed by President Ronald Reagan and the Soviet Union's Mikhail Gorbachev back in 1987. Meanwhile, the Strategic Arms Reduction Treaty ー a nuclear arms reduction treaty between the U.S. and Russia ー is set to expire in 2021, with uncertain prospects for renewal.

Further escalating fear of nuclear conflict is that "basically all nuclear-weapons possessive states are in the midst of modernizing their nuclear arsenals, and making them more precise," Elena Sokova, the deputy director of the James Martin Center for Nonproliferation Studies, told Cheddar. She adds that countries' commitment to first-use doctrine, which holds that states will only use nuclear weapons in response to another state's use of nuclear weapons, is deteriorating.

"Countries, including the United States and the Russian Federation, have really increased the threshold for the use of nuclear weapons in their military doctrines," said Sokova. "It doesn't have to be a nuclear attack that may warrant a response with nuclear weapons. It's very unclear what situation would qualify for that."

More advanced technology, including sophisticated cyber attacks and artificial intelligence, has also exacerbated the possibility of nuclear conflict. Sokolov added that "we have a situation where methods of controlling these nuclear weapons could be subject to manipulation."

She explained that communications methods for controlling nuclear weapons — or satellites that help monitor them — could be hacked. Non-state actors could also manipulate or falsify data that report on nuclear activity.