Anne Richard, US Assistant Secretary of State for the Bureau of Population, Refugees and Migration, said Washington had called on rebels fighting in Sudan's South Kordofan and Blue Nile states to end militarization of the Yida refugee camp.
“We have asked them not use the camp, which is supposed to be civilian, as a center for R&R (rest and recuperation) or for recruitment of soldiers,” Richard told reporters after a visit to Yida, in South Sudan's Unity state.
“Especially, we’ve asked that they not take children to serve as soldiers on the other side of the border," she added, speaking in South Sudan’s capital.
The Sudan People’s Liberation Movement-North (SPLM-N) has been fighting government forces since June 2011 for greater autonomy.
The insurgents were allies of then southern rebels during Sudan’s 1983-2005 civil war, which ended with a peace deal that led to South Sudan's independence in July last year.
Sudan has repeatedly accused former civil war enemies in South Sudan of supporting the SPLM-N and allowing the insurgents to set up rearguard bases, a charge which analysts believe despite denials by the government in Juba.
Richard’s comments are the first time a senior Western official has said the SPLM-N are operating inside South Sudan.
Richard said the overcrowded Yida camp -- home to over 60,000 refugees from Sudan who have fled hunger and aerial bombardment -- should be moved further south and away from the border.
“The Yida camp was bombed a few months ago, there are a lot of movements in that border area of military combatants,” she said.
“According to international standards, refugee camps are supposed to be run for and by civilians,” Richard explained, saying that they had seen “uniformed military in the camp”.