"REARMING"
The SPLM has consistently raised doubts about the sincerity of the NCP, saying it has been implementing the Comprehensive Peace Agreement (CPA) selectively and has tried to renegotiate some aspects of the text.
The most contentious issues include the protocol on the oil-rich Abyei area, demarcation of the north-south border and withdrawal of northern forces from the south.
SPLM officials also accuse the NCP of withholding funds for a census crucial for elections in 2009 and a referendum on the secession of the south in 2011.
On Monday, Kiir said the peace deal was at risk.
"I am alarmed, worried and deeply concerned about the status of CPA implementation," he told the parliament in Juba, capital of south Sudan.
"I am worried Mr. Speaker that it is likely that Sudan will revert again to war if we do not act now with our partner NCP."
An NCP spokesman declined immediate comment on the latest developments. The NCP has previously denied SPLM allegations it is stalling on the deal and said implementation is going well.
SPLM officials have issued similar warnings in the past, but the ICG's Mozersky said, "it seems to be coming up with increasing regularity".
Smith said the statement was Kiir's "strongest criticism ever" of the pace of implementation of the peace deal and that both sides seem to be gearing up for the worst.
"The reality there is that both sides have been rearming over the past two years, which indicates that they do not have much faith in peace process," he said.
Could the country slip back into a north-south war as Kiir suggests? "I don't think one can rule that out," Smith said.
