UNITED NATIONS (Reuters) - The United States warned South Sudan’s government on Thursday that preventing humanitarian aid workers from reaching parts of the war-torn state that are suffering famine could “amount to deliberate starvation tactics.”

Slideshow ( 6 images )

A civil war erupted in 2013 when President Salva Kiir, an ethnic Dinka, fired his deputy, Riek Machar, a Nuer, who has fled and is now in South Africa. The United Nations says at least one-quarter of South Sudanese have been displaced.

The United Nations has declared a famine in some parts of South Sudan, where nearly half the population - some 5.5 million people - face food shortages. But the country recently hiked work permit fees a hundredfold for foreign aid workers, to $10,000.

“The famine is not a result of drought, it is the result of leaders more interested in political power and personal gain than in stopping violence and allowing humanitarian access,” Deputy U.S. Ambassador Michele Sison told the Security Council.

“The government’s continued unconscionable impediments to humanitarians seeking access to famine-stricken populations may amount to deliberate starvation tactics,” she said.

Russian Deputy U.N. Ambassador Petr Illichev disagreed, saying the famine was “linked not just to problems with security, but also with inclement weather conditions.”

The Security Council said in a statement that it was “deeply concerned about the actions of all parties to the conflict that are perpetuating the humanitarian crisis.” However, the language was toned down from a draft that said the crisis was “the result of the actions of all parties to the conflict.”

South Sudan Deputy Ambassador Joseph Mourn Majak Ngor Malok rejected accusations that the government was to blame for the famine, saying “it will spare no efforts to help address the situation and calls upon the international community to assist in addressing this urgent matter.”

Sison’s remarks give the first indication of how President Donald Trump’s administration views the crisis in South Sudan.

The previous administrations of President George W. Bush and President Barack Obama were heavily involved in the birth of South Sudan, which signed a peace accord with Sudan in 2005 and gained independence in 2011.

“I wouldn’t characterize South Sudan as their top priority by any means, but I think it is positive and constructive... that they are planning to carry on being the lead in the Security Council,” said a senior U.N. diplomat, speaking on condition of anonymity.