The Group of Seven leaders are set to pledge at their summit in Hiroshima later this week to bolster the regime established by the Nuclear Non-Proliferation Treaty to promote disarmament, a diplomatic source said Tuesday.

The commitment in an outcome document will highlight the importance of nuclear countries disclosing their capabilities and continuing efforts to reduce the number of weapons, while positioning the NPT as the foundation for non-proliferation, the source said.

Nuclear disarmament is expected to be discussed at a session on the first day of the three-day summit through Sunday in the western Japanese city devastated by a U.S. atomic bomb in August 1945, the source said. The document is likely to be issued on Friday.

Photo taken in Hiroshima on May 16, 2023, shows a police officer on guard at the Peace Memorial Park ahead of G-7 summit in the western Japan city. (Kyodo) 

The document will reflect the dedication of Prime Minister Fumio Kishida, the chair of the G-7 summit, to nuclear disarmament amid concerns over Russia's use of such weapons in its war against Ukraine and China's increasing nuclear stockpile.

Kishida, who represents a constituency in Hiroshima, said Monday that the G-7 leaders will "send out a strong message to realize a world free of nuclear weapons."

Before they begin their talks, the G-7 leaders are set to visit the Hiroshima Peace Memorial Museum, which serves as a testament to the world's first nuclear attack in the final days of World War II, the source said.

The NPT came into effect in 1970. The treaty designates five nations -- Britain, China, France, Russia and the United States -- as authorized possessors of nuclear arsenals, while prohibiting other countries from acquiring them.

Represented by Moscow's suspension of its participation in the New START treaty in February, the only remaining nuclear arms control pact with Washington at that time, talks on nuclear disarmament have shown little progress worldwide in recent years.

The NPT review conference failed to adopt a consensus report in 2015 and 2022, while nations such as North Korea and Iran are believed to be continuing their nuclear development.

In the outcome document, the G-7 countries will promise to oppose the use and threat of nuclear arms and call on political leaders from around the world to visit Hiroshima and Nagasaki, the other Japanese city struck by a U.S. atomic bomb, the source said.

The document will also express appreciation for the five pillars of the "Hiroshima Action Plan," aimed at achieving a world free from nuclear weapons, that Kishida announced in August last year during a speech at the NPT review conference in New York.

At the Hiroshima summit, six outcome documents are being arranged with the themes of general summary, nuclear disarmament, Ukraine, economic security, clean energy and food security, the source said.

Food security will be discussed at an "outreach" session that will also include the leaders from eight invited nations -- Australia, Brazil, Comoros, Cook Islands, India, Indonesia, South Korea and Vietnam, the source added.