House Speaker Nancy Pelosi is set this week to be the highest-ranking sitting US official to visit the site of the Hiroshima atomic bombing, which bitterly divides opinion six decades later.

No sitting US president or vice president has ever paid respects to the dead of the US nuclear attacks on Hiroshima and Nagasaki in 1945, a sore point for many survivors in Japan.

Pelosi will travel to Hiroshima for a meeting of parliament speakers from the Group of Eight major industrial nations. Pelosi, who is second in line to the presidency, is a member of Barack Obama's Democratic Party.

On Tuesday, Pelosi and the other speakers will lay flowers at a memorial in Hiroshima, hear testimony from a bomb survivor and hold discussions on disarmament, according to Japanese officials.

Kota Kiya, who was four years old when the atomic bomb devastated his hometown, welcomed the visit but said he hoped the leaders of nuclear weapons states would come instead.

"We wish that top leaders would visit Hiroshima and Nagasaki while they are in power, at least once, to see the atrocity of the nuclear bombings," said Kiya, secretary general of the Hiroshima chapter of Hidankyo, the group of atomic bomb survivors.

On August 6, 1945, a single US bomb instantly killed more than 140,000 people in Hiroshima and injured tens of thousands more with radiation or horrific burns.

The United States dropped a second nuclear bomb on Nagasaki three days later, killing another 70,000 people. Japan surrendered less than a week later, ending World War II.

In Japan, it is an article of faith that the nuclear bombings were wrong. Last year, a defence minister was forced to resign after saying the attacks were inevitable.

In the United States, the decision to carry out history's only nuclear attacks is more controversial, with many war veterans arguing the bombings prevented a ground invasion of Japan that would have cost many more lives.

"Any high-ranking official visiting an atomic site can only help to heighten awareness about the horror of nuclear weapons or power," said Bonnie Urfer, co-director of US anti-nuclear group Nukewatch.

"Hawks within the US government can be expected to criticise House Speaker Nancy Pelosi while doves may quietly applaud the move," Urfer said.

The Hiroshima visit was the work of Japan's lower house Speaker Yohei Kono, a veteran politician who has long taken exception to Japan's gradual drift away from its post-World War II pacifism.

The liberal Asahi Shimbun hailed Kono in an editorial last week, calling Pelosi's visit to Hiroshima "very significant" in light of the "wide gap in perception between Japan and the United States" on the nuclear bombings.

The G8 comprises Britain, Canada, France, Germany, Italy, Japan, Russia and the United States.

Hiroshima and Nagasaki regularly invite world leaders to visit, hoping to spread their message for the abolition of nuclear weapons.

China for the first time took part in Hiroshima's annual ceremony on August 6 this year. It left Britain, France, North Korea and the United States as the declared nuclear states never to have attended.

While no sitting US presidents have visited the Hiroshima memorial, both Jimmy Carter and Richard Nixon went in a private capacity when they were not in office.