Yemeni delegates Monday were close to agreement on the shape of a future federal state to settle a long-standing dispute over the south's status, sources close to a national dialogue said.
But the sealing of a deal was postponed after ousted president Ali Abdullah Saleh's two representatives walked out of a 16-member committee handling the north-south issue, refusing to sign an agreed document.
Committee members were to sign the accord to achieve a "just solution that would preserve the security and stability of a united Yemen on a federal and democratic basis," according to the text of the document received by AFP.
"We were supposed to sign the agreement today (Monday) but that has been postponed," committee spokesman Mohammed Qahtan told AFP.
Long-serving Saleh, who was forced to step down in 2012 following a year of nationwide demonstrations, is accused of seeking to impede the dialogue, stipulated by a UN-backed plan that saw him out of office.
Saleh's General People's Congress, on the party website, slammed "violations" taking place in the national dialogue, in reference to the north-south panel, and rejected any bid to "harm the unity of the homeland."
Foreign Minister Abu Bakr al-Kurbi told AFP last week that participants in the reconciliation talks had agreed on the principle of changing the Arab republic into a federal state.
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But differences remain on the number of regions, he said.
Southern delegates to the dialogue have been demanding a federal state consisting of north and south Yemen, while northerners are proposing more than two entities, according to the sources close to the talks.
In Monday's document, the regions would have broad administrative, executive, legislative and economic powers.
Regional authorities will also decide on the exploration and management of natural resources, in cooperation with the federal government. But these resources would remain under state ownership.
During a transitional period before a federal government is set up, southerners would occupy 50 percent of posts in Yemen's official structures, including the executive, legislative and judicial branches, as well as in the security forces.
Four years after north and south Yemen united in 1990, a short-lived southern breakaway sparked a civil war that culminated in the south's occupation by northern troops.
The southern question has been a major stumbling-block for the national dialogue launched in March, with hardline factions of the Southern Movement demanding secession, boycotting the talks.
The dialogue, aimed at drawing up a new constitution and preparing for elections in February, were scheduled to end on Wednesday but have been extended by a month.
Yemen is the only Arab Spring state in which an uprising resulted in a negotiated solution, with Saleh agreeing to step down.