The deteriorating humanitarian situation in the world's youngest nation, South Sudan, has been a key focus of talks in Kenya between US Secretary of State, John Kerry, and regional foreign leaders.
The breakdown of a fragile peace deal last month saw fierce fighting erupt in the capital, Juba, and raised fears the country could slide back into civil war.
More than two years of conflict had pitted troops loyal to President Salva Kiir against those of his former deputy Riek Machar.
John Kerry described events in South Sudan as tragic, and in some cases reprehensible.
"Warring parties have terrorised and abused non-combatants, especially women and girls, and more than 2.5 million people have been forced to leave their homes. 40 per cent of the population is without enough food and they're witnessing record levels of inflation in their economy. So help is urgently needed in order to save lives."
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The US Secretary of State pledged US$138 million in additional aid to provide food, water and medicine to those in need.
The US is South Sudan's biggest international donor, with the more than US$1.5 billion given since late 2013 vital to its emergence as a nation.
But Mr Kerry warned that funding would cease if South Sudan's leaders failed to halt the violence.
"We made it crystal clear that this is not forever: we are not just going to fill in a void, we're not just going to provide help incessantly if they're not willing to accept responsibility and do the things necessary to deliver to their people. The leaders of South Sudan have to live up to their responsibilities. They have to put the interests of their citizens first and they have to refrain from violent and provocative acts. And the time has come to replace confrontation and impunity with reconciliation and accountability."
The United Nations alleges government forces were responsible for much of the violence against civilians.
Earlier this month, South Sudan rejected a vote by the UN Security Council to deploy 4,000 additional peacekeepers to help restore calm.
A 12,000-strong UN mission is already in place, and South Sudan's neighbours have been pushing for it to be bolstered.
Mr Kerry says there is absolutely no question that a regional protection force should be deployed.
"And let me emphasise; this is not an intervention force. This a protection force with a very clear mandate: to be able to protect people for their access, their freedom of movement and their ability to remain free from attack or ambush from any source whatsoever. It is supplementary to the sovereignty and the efforts of South Sudan itself."
He did not give a timeline for the deployment, but said the foreign ministers had agreed on the immediate implementation of meetings and steps to guarantee momentum.
Mr Kerry also committed funds to help Kenya with next year's elections, and support for refugees and drought victims in the region.
From Nairobi, Mr Kerry will travel to Africa's most populous nation, Nigeria, to speak with the country's president about tackling corruption in the face of a weakening economy.
He will also meet with leaders from the country's north, where the militant group Boko Haram continues to carry out attacks.
