NHK has learned of new video footage found in Hiroshima City of an interpreter testifying that J. Robert Oppenheimer shed tears as he said "I'm sorry" to atomic bomb survivors 60 years ago.

Oppenheimer was a theoretical physicist who directed the US project to develop the atomic bomb during World War Two.

He is said to have been pained by the devastation caused by the atomic bombings of Hiroshima and Nagasaki. But he reportedly did not visit the cities when he made a trip to Japan in 1960.

The footage, which was in the possession of a Hiroshima-based non-profit organization, shows interpreter Teichler Yoko speaking in 2015 about a 1964 visit to the US by atomic bomb survivors -- known as hibakusha.

Teichler describes a closed-door meeting between Oppenheimer and fellow theoretical physicist Shono Naomi, a Hiroshima-born hibakusha, and other Japanese visitors.

She says when they went into the room to meet Oppenheimer, he already had tears streaming down his face and he repeatedly said "I'm sorry."

Shono wrote about the meeting in his high school alumni newsletter. He noted Oppenheimer said he did not want to talk about Hiroshima and Nagasaki, and that those words conveyed the burden he had been carrying.

Miyamoto Yuki, a professor at DePaul University in Chicago, says it is surprising -- and hugely significant for the hibakusha -- that Oppenheimer actually met them and said sorry.

Miyamoto says many of the survivors may have hoped that Oppenheimer would act on his words and campaign to abolish nuclear weapons, but unfortunately he did not do so. He died in 1967.

She says it may have been difficult for him because at the time many Americans supported nuclear deterrence.

Miyamoto adds that abolishing nuclear weapons remains a challenge we must undertake, saying we must close the gap between Oppenheimer's words and reality through our actions.