Papua New Guinea Prime Minister James Marape says his nation does not deserve to be labelled cannibals, and urged the US to clear up the remnants of the Second World War littered across the Pacific, after comments by President Joe Biden about his missing serviceman uncle.

Biden had "appeared to imply his uncle was eaten by cannibals after his plane was shot down over PNG during WWII", Marape's office said in a statement late on Sunday.

"President Biden's remarks may have been a slip of the tongue; however, my country does not deserve to be labelled as such," Marape said in the statement.

"I urge President Biden to get the White House to look into cleaning up these remains of WWII so the truth about missing servicemen like Ambrose Finnegan can be put to rest."

Biden has previously cited his personal connection with Papua New Guinea's wartime history on visits to Australia, telling the story of his uncle who died in a plane crash in May 1944.

Biden last week raised the possibility his uncle might have fallen victim to cannibals, after visiting a missing-in-action war memorial in Pennsylvania.

Historians say Papua New Guinea was crucial to the United States drive across the Pacific to liberate the Philippines in the Second World War, while Australia has said the wartime history showed the renewed strategic importance of its northern neighbour.

The impact of the war remains sensitive among Pacific Islanders, however. Marape said his nation was "needlessly dragged into a conflict that was not their doing".

Papua New Guinea and Solomon Islands remain littered with wartime human remains, plane wrecks, ship wrecks and tunnels, as well as leftover bombs which were still killing people, he said. (Reuters)