A Catholic aid network has warned of a 'forgotten crisis' in South Sudan and said the country is 'heading towards a scenario of despair'.

The warning issued by Caritas comes as violence has flared again with the approach of peace talks aimed at resolving the civil war that has lasted since 2013. Observers say rival groups are jockeying to be in a favourable position when delegates reach the negotiating table.

The war has led to around 2 million people fleeing as refugees to neighbouring countries and another 2 million becoming internally displaced. Famine and disease are widespread and government has collapsed across large parts of the country.

'People are living in constant fear and insecurity, suffering mentally, physically and are starving,' Caritas South Sudan and its partners, which include CAFOD and Trocaire, warned after a meeting this month in the capital, Juba. 'In the coming months heavy rains will add to the already untold suffering for the people.' A statement issued by the local president of Caritas, Bishop Erkolano Lodu Tombe of Yei, says South Sudan is becoming a 'forgotten crisis'.

Forces loyal to President Salva Kiir and followers of the former vice president, Riek Machar, have been augmented by local militias joining the fighting. The Caritas statement calls for an end to tribal manipulation, which is fuelling violence between communities. 'Politicised tribalism safeguards the vested interest of a few, over and above the needs of the innocent population,' the aid officials say.

While precise figures are hard to come by, the UN estimates that between 50,000 and 300,000 people have been killed and many more injured in the conflict. Around 85 per cent of refugees are women and children.

As well as local famines, much of South Sudan is affected by cholera and the UN has warned that more than 7 million people, almost two-thirds of the population, will not be able to feed themselves without sustained humanitarian intervention.

In a sign of international frustration with South Sudan, the US said this week it would review its assistance programs because it could not continue a partnership with leaders perpetuating 'endless war'.

South Sudan's foreign affairs spokesman Mawien Makol Ariik said: 'We are asking the United States not to abandon this country because we need them...their role to assist the population of South Sudan is crucial and cannot be ignored.'

The US is the largest aid donor to South Sudan. The White House said on Tuesday it had been a 'proud and hopeful supporter' when it gained independence in 2011. 'Seven years later, the leaders of this country have squandered this partnership...killed their own people, and repeatedly demonstrated their inability and unwillingness to live up to their commitments to end the country's civil war,' it said.