Nairobi - South Sudan's rebels warned on Tuesday the government risks a "return to war" by ordering an increase in regional states and undermining the power sharing clauses of a peace deal.
President Salva Kiir on Friday ordered the number of regional states be nearly tripled from the current 10 to 28, rendering the agreed power sharing formula redundant.
"The objective of this unilateral decision is to arouse tribal sentiments in the people of South Sudan, so that there can be a return to war," said rebel spokesman Mabior Garang.
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Garang warned it "would effectively cause the collapse" of peace deal.
Kiir, who has been fighting to crush a rebellion since December 2013 in which tens of thousands have been killed, the economy destroyed and war zone regions pushed to the brink of famine, signed a peace agreement in August to end the war.
Months of negotiations
The army and rebels have repeatedly traded blame, accusing each other of breaking the ceasefire, the eighth such agreement to have been signed.
Months of negotiations led to the internationally-brokered deal, including a transitional government and a complex power-sharing formula in which rebels get a share of seats at national and state levels.
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The rebels, led by former vice president Riek Machar, also choose the powerful governor posts in the northern battleground states of Unity and Upper Nile, the country's main oil production zones.
The government order says the expansion - which sees the three key states of Unity, Upper Nile and Jonglei split into 10 - is to "devolve power" to the people.
Widespread rape, torture
"This is just another attempt by [some elements in] the Salva Kiir administration to derail the peace agreement," Garang said.
"This is the only thing that can bring our republic back from the abyss."
Both sides are accused of having perpetrated ethnic massacres, recruited and killed children and carried out widespread rape, torture and forced displacement of populations to "cleanse" areas of their opponents.
The International Committee of the Red Cross said on Monday it had been forced once again to pull out of its facility in Leer in southern Unity state amid "intense fighting".
It said "dozens of well-organised armed men entered the compound over the weekend and stole equipment, medical supplies and money".