John Kerry will not offer an apology for the United States' use of the atomic bomb against Japan when he becomes the first US secretary of state to visit the Hiroshima Peace Memorial Museum tomorrow, a senior US official said.

Mr Kerry is visiting the city, which was obliterated by a US atomic bomb on 6 August 1945, to attend a gathering of foreign ministers from the Group of Seven (G7) advanced economies.

The US diplomat is to join his counterparts from Britain, Canada, France, Germany, Italy and Japan tomorrow to tour the city's atomic bomb museum and to lay flowers at a cenotaph for its victims - becoming the first in his post to do so.

"If you are asking whether the Secretary of State came to Hiroshima to apologise, the answer is no," a senior US official told reporters today.

"If you are asking whether the Secretary and I think all Americans and all Japanese are filled with sorrow at the tragedies that befell so many of our countrymen, the answer is yes," the official added.

Mr Kerry's trip could pave the way for an unprecedented visit to Hiroshima by a sitting US president when Barack Obama attends the annual G7 summit to be held in Japan next month.

While saying the White House has yet to make a decision, the senior US official said Mr Obama has shown he is willing to do controversial things such as visiting Havana last month.

The official suggested there was no "great or insurmountable angst about the optics or the politics of a visit to Hiroshima".

He also said there was no Japanese effort to seek a US apology, "nor is there any interest in reopening the question of blame for the sequence of events that culminated in the use of the atomic bomb".

Japanese Foreign Minister Fumio Kishida, who presides over the two-day meeting, said ministers will discuss anti-terrorism steps, maritime security and issues related to North Korea, Ukraine and the Middle East.

Some of the topics discussed today included countering violent extremism, the battle against so-called Islamic State militants and the effort to end the five-year Syrian civil war, a second US official said.

Maritime security is on the cards after China rattled nerves in the region with its controversial reclamation work in the South China Sea. Some talk of nuclear non-proliferation is inevitable given North Korea's fourth nuclear test in January.

During World War II, a US warplane dropped a nuclear bomb on Hiroshima on 6 August 1945 reducing the city to ashes and killing 140,000 people by the end of that year.

Hiroshima's suffering is vividly displayed at the museum that the ministers will tour.

Three days after dropping the atomic bomb on Hiroshima, the United States dropped a second one on Nagasaki. Japan surrendered six days later.