VIENNA – Foreign Minister Fumio Kishida called on the international community Tuesday to strengthen the nuclear nonproliferation regime, citing the growing threat posed by North Korea’s nuclear and missile programs.

Taking part in the preparatory committee for the 2020 review conference of the Nuclear Non-Proliferation Treaty in Vienna, the first Japanese foreign minister to do so, Kishida also urged cooperation between nuclear states and non-nuclear states to prevent the spread of nuclear arms.

“North Korea has conducted two nuclear tests and launched more than 30 ballistic missiles since last year. Its nuclear and missile development has reached a new level and is posing a real threat to the region and beyond in the international community,” Kishida told the committee.

Kishida, a veteran House of Representatives lawmaker from Hiroshima, which was devastated by a U.S. atomic bombing in 1945, condemned North Korea’s aggressive pursuit of nuclear development as posing a “challenge” to the disarmament and non-proliferation regime under the treaty.

The efforts toward a world without nuclear weapons should be “carried out in a realistic manner, while taking into account the security environment that is becoming increasingly severe, including that of North Korea,” Kishida said.

The first session of the committee to prepare for the review conference in 2020 was held as countries remain at odds over a separate treaty on banning nuclear weapons.

Japan has said it aspires to a world free of nuclear weapons but will abstain from the U.N. negotiations in March for a treaty on a ban, alongside the five recognized nuclear weapons states — Britain, China, France, Russia and the United States.

Regarding the U.N. talks for a treaty on a ban, Kishida told the committee it would further deepen the gap between nuclear states and non-nuclear states, calling for a gradual approach to reducing nuclear weapons, which would be “realistic.”

The government’s decision, seen as reflecting its reliance on the U.S. nuclear umbrella, triggered criticism from the survivors of the U.S. atomic bombings of Hiroshima and Nagasaki, who saw the first-ever U.N. talks on the treaty as a step toward achieving a world free of nuclear weapons.

The United States echoed Japan’s views on the growing North Korean threat. “Well-intentioned diplomatic efforts over the last 20 years to halt the DPRK’s proscribed programs have failed,” Robert Wood, permanent representative of the United States to the Conference on Disarmament, told the session, using the acronym of North Korea’s formal name, the Democratic People’s Republic of Korea.

“The threat of a North Korean nuclear attack on Seoul or Tokyo is real, and it is only a matter of time before the DPRK develops the capability to strike the U.S. mainland,” Wood said.

With nuclear states claiming a treaty on a ban would undermine the non-proliferation regime under the NPT, many participants —including Mexico, which is leading the effort to outlaw nuclear weapons — do not plan to focus on it in the preparatory committee session through May 12 in the hope of making progress on the review conference.

Mexican Ambassador to Austria Alicia Buenrostro said in a recent interview that there is “common ground and good spirit” to make the 2017 preparatory committee “really work out” with a “more transparent and balanced process.”

Some members seeking a treaty on a ban are expected to contend that it would be in line with the NPT, under which nuclear powers are supposed to work toward the disarmament of their nuclear arsenals.

Buenrostro said Mexico’s stance is that nuclear states should show a more decisive commitment to disarmament.

The previous 2015 review conference fell apart, with parties failing to adopt a final agreement, largely due to a rift between the United States and Arab countries over discussions on efforts aimed at denuclearizing Israel, a non-NPT member.

The document would have produced an outline for action over the next five years.