Nuclear test refugees from Bikini Atoll in the Marshall Islands are now fleeing the effects of climate change on their second home, Kili Island.
The Bikini Island Council is appealing to the US for financial help with relocation after repeated king tide flooding and storm surges over the past four years on Kili.
The liaison officer for the people of Bikini, Jack Niedenthal, said the Marshalls' Compact of Free Association, the US military airbase and historical ties, meant the US had a moral obligation to help the community of 700 people, who are facing homelessness.
"There's a promise that they made to Bikinians, that the older people that I've known over the years recite like it's right out of the Bible," he said.
"This American stood up to them, Commodore Wyatt in 1946, and said 'Don't you worry. It doesn't matter if you're adrift on a raft at sea or on a sand bar, you will be like the children of America. We are going to take care of you.'"
Mr Niedenthal said a third of the homes on Kili were now empty as people escaped the island.
The local population has lived in exile since the start of US nuclear testing at Bikini in 1946.
The US tested 24 nuclear weapons at Bikini, including its largest hydrogen bomb, Bravo, at 15 megatons in 1954.
The Resettlement Trust Fund for the People of Bikini was established in 1982 by US public law, to be used for relocation within the Marshall Islands.