The fate of over 4.7 million people living on the brink of famine in northeast Nigeria is hanging in the balance.

According to the United Nations' World Food Programme supplies could in a few weeks run out of funding to feed them.

Four people familiar with the matter said the situation is intensifying one of the world's largest humanitarian crises.

Most of the persons are displaced in the heat of Islamist insurgency perpetrated by Boko Haram and they need rations to survive, according to the World Food Programme (WFP), one of the main aid groups handing out food.

Many of those living in camps for displaced people say they already barely get enough to eat.

"With the money they have right now, and if they won't cut rations, they can only go to May 18," one person told Reuters, citing talks with the WFP, who asked to not be named because they were not authorised to speak to media.

The WFP was "reasonably certain" it would get enough funding to last until late June, the person added.

"All humanitarian crises globally are woefully underfunded and for WFP Nigeria is in one of the worst situations for funding," a WFP spokeswoman said.

"We are trying to save lives. We need over the next six months $207 million for Nigeria. At the moment, the programme is 13 per cent funded for 2017. It's extremely low. Of the four countries facing famine it is the least funded."

The conflict with Islamist insurgency Boko Haram, which seeks to establish a caliphate in Nigeria's northeast, began in 2009 and shows no sign of ending. It has killed more than 20,000 people and displaced more than two million.

Nigeria's northeast is now teetering on the brink of famine, aid organisations say, pointing to two years of missed crop harvests in what was once a breadbasket for the country, and the high likelihood of missing a third.

The approaching rainy season increases the risk of disease spreading, especially within camps for the displaced, adding more stress to efforts to respond to the humanitarian crisis.

The wet season also means tens of thousands of refugees are attempting to return home to farm, despite facing serious dangers, saying there is not enough food provided in the camps to sustain them.

In a meeting on Monday with the WFP in Nigeria's capital Abuja, donor countries and organisations, criticised the group for not having a satisfactory contingency plan if funding starts to dry up, two of the people with knowledge of the talks said.

The WFP spokeswoman said meetings with donors were genial, open and frank.

"When we are funded and able to get out to the field we are getting to people. This crisis can be averted and we want people to understand this will work if it's funded. We can avert the famine."

The U.S. Embassy in Abuja said the U.S. government was working "urgently and cooperatively with our partners in an effort to address the critical humanitarian needs in northeastern Nigeria".

"There is not adequate funding to sustain the global response to those needs here. Additional resources must be found urgently so that feeding does not stop," the embassy said in emailed comments to Reuters.

The WFP and donors have also locked horns over who is to blame for the lack of funding reaching the aid organisation, with the U.N. agency saying the money promised has not been released to them and donors arguing that basic paperwork still has not been submitted, the two people said.