The head of disarmament at the United Nations warned the international community on Tuesday that the threat of nuclear weapons use has increased because the headway made in the post-Cold War era toward denuclearization has “come to a halt.”

“The disarmament and arms control framework upon which the gains of the post-Cold War era were made is eroding, but we have nothing else yet with which to replace it,” Izumi Nakamitsu, the U.N. undersecretary general and high representative for disarmament affairs, told Security Council members.

The warning was issued at a meeting to discuss the 1970 Nuclear Non-Proliferation Treaty ahead of the next NPT review conference to be held in 2020, when the landmark pact marks the 50th year since its entry into force. The NPT is reviewed every five years.

“As a result, the prospect of the use of nuclear weapons is higher than it has been in generations,” Nakamitsu said.

In February, the United States said it is withdrawing from the 1987 bilateral Intermediate-Range Nuclear Forces Treaty with Russia in response to alleged violations by Moscow, a move that could fuel concerns about a new arms race possibly involving other parties such as China.

The situation has been further exacerbated by the trend of nations increasingly modernizing their nuclear arsenals, as well as relying more on rapidly emerging technology that makes acquiring the dangerous weapons easier, the undersecretary general said.

The unstable situation is further compounded by the emergence of regional hot spots that “heighten proliferation drivers,” she added.

“Together, these developments are placing the NPT under increasing stress and are exacerbating the fault lines that have been clearly evident between state parties for some time now,” she added, noting how the next review conference will be a “defining moment.”

Widely recognized as the cornerstone of the international nonproliferation regime, the NPT relies on the pledge by five nuclear powers to work toward disarmament of their nuclear arsenals in exchange for the promise by nonnuclear nations not seek to acquire them, while making nuclear energy for peaceful purposes accessible to any country that wants it.

However, nonnuclear countries that have held to their promise have been increasingly frustrated by what they view as lack of progress toward disarmament by the five nations — Britain, China, France, Russia and the United States — that possess nuclear weapons and are also permanent members of the Security Council.

Additionally, countries such as North Korea, Pakistan, India and Israel, which remain outside the treaty, have pursued nuclear activities in ways that have greatly elevated global concerns.

In the run-up to the NPT review conference to be held for a month from April 2020, a preparatory meeting through May 10 will get underway later this month at the U.N. headquarters.