Chapala Barman is heartbroken as she contemplates leaving the home she has known all her life ahead of a historic land swap between Bangladesh and India that will divide her family.



The exchange at midnight today will end one of the world's most intractable disputes that has kept thousands of people in limbo for nearly 70 years.



But it will also rip apart families like Barman's, leaving some stranded on one side of the border while relatives relocate to the other.



The 60-year-old Hindu is preparing to leave her home in Dahala-Khagrabari, a small island of Indian land inside Muslim-majority Bangladesh, with three of her sons.



She will have to leave four other grown-up children and their families behind in Dahala-Khagrabari, which is about to become part of Bangladesh.



Her three daughters have married Bangladeshis, making them ineligible to move, like her eldest son who was not counted in a joint census of the enclaves conducted in 2011.



"These days I can't stop my tears thinking how can I live without them," Barman told AFP ahead of the handover.



"My grandsons call me by mobile phone, saying 'grandma, please don't go'. My heart pounds with fear when I hear a mobile phone calling."



The two nations will hoist their respective flags in 162 enclaves -- 111 in Bangladesh and 51 in India -- at one minute past midnight (1801 GMT Friday) to assume sovereignty over the territories following a border agreement in June.



For many of the 50,000 people living in the enclaves the exchange means an end to 68 years of struggle, cut off from their national governments and unable to access vital services like hospitals and schools.



But it has also meant choosing between staying put and adopting a new nationality or leaving the homes where their families have lived for generations.



The vast majority will stay. But around 1,000 people on the Bangladesh side have opted to keep their Indian nationalities, meaning they will have to relocate by November.



In Dahala-Khagrabari, around 400 kilometres north of Dhaka, Muslims who had chosen to become Bangladeshi citizens were rehearsing their new national anthem and preparing to celebrate.



But in Hindu-dominated parts of the enclave, the atmosphere was tinged with fear and uncertainty.