Joe Biden is due to become the second sitting U.S. president to visit Hiroshima, a city razed by an atomic bombing at the end of World War II, with the international community taking a keen interest in what message, if any, he will deliver on nuclear disarmament.

Unlike Barack Obama, who left his mark on history by visiting the Japanese city in 2016, the primary reason for the current U.S. leader to travel there is to attend this year's three-day summit of the Group of Seven advanced economies from May 19.

Daryl Kimball, executive director of the Arms Control Association, is pictured during an interview on April 18, 2023, in Washington. (Kyodo) 

But as Russia's ongoing war in Ukraine gives a chilling warning that the world may be entering a more perilous era, advocates of arms control say it will be a tragic lost opportunity if Biden does not demonstrate a clear commitment to realizing a world without nuclear weapons.

His trip comes after Russia's repeated threats to use tactical nuclear weapons in the war, now in its second year, and amid North Korea's incessant efforts to advance its nuclear and missile development programs.

"It's crucial that (the G-7 leaders) acknowledge and recognize the decades-long impacts of the bombings on the people who were there in 1945 and their descendants, because that is a powerful reminder of why such attacks cannot be repeated today," said Daryl Kimball, executive director of the Arms Control Association.

Kimball, who has been leading the Washington-based organization for over two decades, said Biden and other G-7 leaders do not necessarily need to state anything new, but they should at least collectively demonstrate a serious commitment to nuclear disarmament.

A month before their summit, he and more than 20 other nuclear policy experts, including Ben Rhodes, a former U.S. deputy national security adviser who drafted Obama's historic Hiroshima speech, submitted a letter to Biden urging him to deliver his own address in the city separate from any joint leaders' statement.

Kimball said it would not have to be an "apology" or a "judgment about whether the United States should have dropped two atomic bombs" on the Japanese cities of Hiroshima and Nagasaki in August 1945.

Rather, he said, it is important to offer "a recognition of the fact" of the bombings so as to "help reinforce the taboo against nuclear weapons use and threats of use."

He added Biden should present "specific, pragmatic and practical" options to head off a new arms race, in contrast to Obama, who delivered a "philosophical" address.

The letter submitted to the 80-year-old president on April 19 calls on him to "elaborate on how the United States is willing and ready to work with other states" including those such as China and Russia that possess nuclear weapons.

Biden formally announced his re-election bid late last month. Despite continuing concern about his age, Biden, already the oldest-ever U.S. president, is still favored in a possible rematch against his predecessor Donald Trump in 2024.

People light candles during an event marking the second anniversary of the United Nations treaty banning nuclear weapons in front of the Atomic Bomb Dome in Hiroshima in western Japan on Jan. 22, 2023. (Kyodo) ==Kyodo

The Pentagon said last fall in a policy paper, "By the 2030s the United States will, for the first time in its history, face two major nuclear powers as strategic competitors and potential adversaries," referring to China and Russia.

Yet, since taking office in 2021, Biden has not outlined his overall vision or spoken head-on about how to minimize nuclear dangers.

Many believe there is no more ideal place than Hiroshima to augment the powerful campaign promise Biden made on Aug. 6, 2020, when the former vice president under Obama marked the 75th anniversary of the world's first atomic bombing.

"As president, I will restore American leadership on arms control and nonproliferation as a central pillar of U.S. global leadership," said the then-presumptive Democratic presidential nominee.

Nearly three years later, it remains unclear if Biden can repeat or upgrade his pledge, given that his administration and most legislators on both sides of the aisle now perceive the U.S.-led security architecture as increasingly contested in Asia and elsewhere.

Biden and South Korean President Yoon Suk Yeol agreed to bolster Washington's so-called extended deterrence commitments in late April to deal with North Korea, which continues to test more advanced nuclear delivery systems, including intercontinental ballistic missiles.

While Yoon reaffirmed South Korea's existing nonproliferation commitments, the agreement was a candid admission that the United States relies on nuclear weapons to make credible its commitments to defend South Korea and other allies.

"East Asia is an increasingly dangerous place," said Jennifer Lind, a Dartmouth College associate professor who is an expert on the region's foreign and security affairs, citing China's rapid build-up of nuclear forces in addition to North Korea's weapons programs.

As Japan and South Korea feel more threatened and seek to beef up deterrence with the United States, Lind said a possible visit by Biden to the Peace Memorial Park in Hiroshima that "features calls for nuclear disarmament would thus be quite out of step with the current security environment."

"But a visit to Hiroshima still can and will be tremendously meaningful" for both Japan and the United States, said Lind, who is also a faculty associate at the Reischauer Institute of Japanese Studies at Harvard University.

Apart from serving as a reminder of "the catastrophe of war" and a chance to mourn those lost, the occasion "celebrates the astounding transformation of our relationship since that dark time," she said.