Tens of thousands of children in South Sudan could die this year without assistance from aid agencies, the United Nations said on Saturday, as it appealed for more than $1 billion to help those hit by six months of civil war.

Fighting that erupted in December has driven 1.5 million people from their homes, and seven million are now at risk of starvation and disease, said Toby Lanzer, U.N. Humanitarian Coordinator in South Sudan.

"Unless fighting ends and people can return to their homes and resume their livelihoods, the situation will continue to worsen," he said at the launch of a plan to support 3.8 million people.

"The consequences could be dire: 50,000 children could die this year if they do not get assistance."

The country’s humanitarian crisis worsened when government forces backing President Salva Kiir and soldiers loyal to his sacked deputy Riek Machar violated the cease-fire signed in May just hours after it took effect.

Lanzer said the bleak situation was further compounded by seasonal heavy rains that have made delivering aid difficult, and living conditions at refugee camps even harder for the South Sudanese.

"Cholera has broken out and malaria is rampant and many children are malnourished. Millions of people need emergency health care, food, clean water, proper sanitation and shelter to make it through the year," he said.

Lanzer said aid groups were so far attending to 1.9 million people and had raised $740 million out of a total $1.8 billion needed by December to address the humanitarian crisis.

"This leaves a gap of just over $1 billion — or only $1.50 per day for each person to be assisted. With sufficient resources, we will be able to do much more," he said.

A U.N. Office for the Coordination of Humanitarian Affairs response plan for South Sudan released on Saturday said that by December up to 1.5 million people would have been displaced within South Sudan and more than 835,000 would have sought refuge in neighboring countries.

Even if a new cease-fire took effect, fighting and displacement had already "shattered the lives of millions of people," Lanzer told reporters in the capital Juba.

Warring parties have been accused of blocking or interfering in relief operations in South Sudan, forcing aid agencies to resort to more expensive airdrops of supplies.

"We need to the waterways to be opened, it costs us 10 times less to deliver relief to some locations by [river] barge than it does to fly supplies into those locations," Lanzer said.

Earlier this week, East African states threatened to slap South Sudan's warring sides with sanctions unless they cease all military operations in the conflict which has sparked fears that it could spiral into genocide.

Wire services