The head of international anti-nuclear group ICAN said Monday that Japanese leadership should not fear the U.S. government's reaction and move to recognize the Treaty on the Prohibition of Nuclear Weapons as the ban marks its third anniversary.

"It's silly to be frightened of the risk coming from what the Americans think about observing or joining the treaty," Melissa Parke, executive director of the International Campaign to Abolish Nuclear Weapons, said in an interview with Kyodo News.

"When you compare that to the risk of nuclear weapons, I think it's important to have some perspective," the former Australian lawmaker's said amid her first Japan visit since becoming ICAN's head in September. She also went to Hiroshima and Nagasaki and met hibakusha atomic bomb survivors, among others.

Melissa Parke, executive director of the International Campaign to Abolish Nuclear Weapons, speaks during a Kyodo News interview in Tokyo on Jan. 22, 2024. (Kyodo)

Although Japan suffered the devastating atomic bombings on Hiroshima and Nagasaki in the closing days of World War II, its government does not recognize the treaty effectively banning nuclear arms. Instead, it backs the Treaty on the Non-Proliferation of Nuclear Weapons while under the U.S. nuclear umbrella's protection.

ICAN won the 2017 Nobel Peace Prize for its work to realize the TPNW. The treaty has been ratified by 70 countries predominantly in the Global South, with Indonesia and Brazil expected to follow suit this year, Parke said.

Neither Japan nor any of the nuclear-armed states are among them, but Parke pointed to the examples of countries such as New Zealand and the Philippines, non-umbrella countries with close military ties to the United States, that have ratified the treaty.

"The U.S. is not going anywhere, it's not going to ditch its relationship with Japan if Japan observes or even joins the treaty," she said. "Japan of all states has an interest in this issue of nuclear weapons, having been bombed by the United States."

Fears of nuclear conflict are high following threats stemming from Russia's invasion of Ukraine and, more recently, nuclear-capable Israel's conflict in Gaza and tit-for-tat missile exchanges between Iran and nuclear-armed Pakistan.

Among recent commitments to deterrence, the May 2023 Hiroshima Group of Seven leaders' summit chaired by Prime Minister Fumio Kishida released a communique on nuclear disarmament upholding the NPT and saying nuclear arms should "serve defensive purposes, deter aggression and prevent war and coercion" for as long as they exist.

While Parke conceded the current global nuclear situation is "a more complex picture than it was during the Cold War," she said more nuclear arms heighten global risk and called deterrence a "circular" argument.

"What we need is global leadership to break out of that cycle of military buildup and constant confrontation because it's leading to proliferation," she said.

According to the Stockholm International Peace Research Institute, as of the start of 2023, nine nuclear powers possessed an estimated 12,512 nuclear weapons. About 2,000 warheads were on high alert status, the same number as a year before.

Despite attempts to arrange a meeting with Kishida, however, Parke on Tuesday instead meets a special advisor behind closed doors.

Reflecting on her visit to Japan, Parke said atomic bomb survivors are the nuclear debate's true realists. "People who call themselves realists and security experts and so forth, they talk in these abstract terms like deterrence and security and stability, but the reality is Hiroshima and Nagasaki and what happened," she said.

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