The United States says it is “gravely” concerned by the declaration of famine in parts of South Sudan.

The US State Department says the “man-made crisis is the direct consequence of a conflict prolonged by South Sudanese leaders who are unwilling to put aside political ambitions for the good of their people”.

An estimated 5.5 million people—nearly half of South Sudan’s population—will face life-threatening hunger this year, according to UN agencies and the South Sudan National Bureau of Statistics.

The catastrophe is said to be worst in the former Unity State where at least 100,000 people are facing starvation.

On Monday, the agencies attributed the condition to “war and a collapsing economy”. Three years of conflict have reportedly severely undermined crop production and rural livelihoods.

“We call on President Kiir to expeditiously make good on his promise that humanitarian and developmental organizations will have unimpeded access to populations in need across the country,” said Acting Spokesperson Mark Toner in a statement issued today.

On Tuesday, the European Union today announced $86.4 million in emergency aid a day after famine was declared in South Sudan.

It said the new humanitarian aid package would be used for the most urgent needs in the country and help neighboring countries cope with the massive influx of refugees.

Both US and the EU are major donors of humanitarian assistance to South Sudan. US alone has provided $2.1 billion since 2014.