"We are also deeply committed, given past lessons, to try to prevent the chaos and the genocide that too often comes of the violence that can occur if things break down," Kerry told reporters in an online discussion.
"We all have an interest - and everybody has an interest - in not letting that happen."
The United States felt "a responsibility" towards the world's newest nation, after midwifing its birth in 2011, America's top diplomat added, speaking as regional mediators opened a new round of peace talks in Ethiopia.
"We believe this is part of the defining of the future of Africa, and we will remain deeply committed and personally engaged in an effort to try to help the people of South Sudan define their own future in peace and prosperity, hopefully."
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The talks, involving representatives of President Salva Kiir and rebel leader Riek Machar, are set to begin in earnest tomorrow morning.
They are aimed at addressing the root causes of the nearly two-month-old conflict in the world's youngest nation.
Washington at the weekend sounded the alarm over repeated violations of a January 23 ceasefire deal, and it called for "the redeployment or phased withdrawal of foreign forces invited by either side."