The insurgents came close to capturing the capital Bangui and overthrowing President Francois Bozize late last year before accepting the peace deal in January under which some of their leaders joined the central government.
But increasingly bitter rhetoric from both sides is threatening to pitch the mineral-rich but impoverished, landlocked country back into conflict.
In a sign of growing tension, the Seleka rebel military command detained five ministers from its side on Sunday, preventing them from returning to the capital after talks with U.N., African Union and European Union officials.
The insurgents have demanded the release of political prisoners and the departure of about 400 South African troops who were sent in to prop up Bozize’s army.
“We are giving Bozize and those around him 72 hours to meet our principal demands, otherwise we will resume hostilities,” Seleka’s spokesman, Colonel Sylvain Bordas, said after a meeting with the international officials in the town of Sibut on Sunday.
“In the meantime, all our ministers in the government will stay here with us. The rest of the delegation may go back to Bangui,” he said.
One of the ministers told French RFI radio on Monday that the military command was detaining them as a means to force Bozize to accept their demands immediately.
The insurgents have also called for the incorporation of 2,000 men from their group into the national army and the recognition of their military ranks.
The government of the Central African Republic was not immediately available for comment.
Chad, Gabon, Cameroon, Republic ofCongoand South Africa have deployed hundreds of troops to shore up Bozize’s army after it suffered a string of defeats, allowing the rebels to advance to within 75 km (45 miles) of Bangui.
The five ministers were being kept at a rebel camp in Sibut, about 185 km (115 miles) from the capital where they discussed with diplomats how to defuse the latest crisis.
The United States said on Sunday it was concerned about worsening security in Central African Republic, urging all sides to implement the ceasefire deal.
Insurgents seized two eastern towns last week, threatening to resume their insurgency if their demands were disregarded.
They previously insisted that Bozize’s resignation was a precondition for peace and that the president, who seized power in a Chadian-backed 2003 coup, should stand trial at the International Criminal Court.
Central African Republic, a former French colony, remains among the least developed in the world despite rich deposits of gold, diamonds and uranium.