Hamadi Jebali of the Islamist Ennahda party was poised Saturday to become Tunisia's new prime minister in the first elected government to emerge from the Arab Spring uprisings.
In a deal struck by the three main parties, to be officially unveiled Monday, Jebali will take the premier's post while Moncef Marzouki of the Congress for the Republic party (CPR), will become president, party sources said.
Mustapha Ben Jaafar, of the third-largest party Ettakatol, will occupy the third key post, president of the constituent assembly.
All three appointments are subject to the approval of the assembly itself when it holds its first meeting on Tuesday.
News of the appointments were confirmed by key figures in the three-party negotiations, including senior CPR figure Abdelwaheb Matar and a senior Ettakatol figure who preferred to remain anonymous.
The deal followed Tunisia's historic democratic elections nine months after the January overthrow of dictator Zine el Abidine Ben Ali, the first ruler toppled in the Arab Spring.
The October 23 poll, the first held as a result of the uprisings that have shaken the region, gave Ennahda (Arab for Renaissance) the most seats in the 217-strong constituent assembly, with 89.
They were followed by the left-wing nationalist CPR with 29 seats, and the leftist liberal Ettakatol (Forum) party with 20.
Jebali, 63, an Islamist, is the moderate deputy leader of Ennahda, whose leader, Rached Ghannouchi, is associated with a more hardline position on Islam.
Jebali's credibility comes in part from the fact that he spent 15 years in Ben Ali's jails. He speaks fluent French and has been at pains to allay fears that his party wants to impose an intolerant brand of Islam.
He stumbled in that task last Sunday, alarming some observers with a reference to "the caliphate", an old system of government based on Islamic sharia law.
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Marzouki, 66, also has a long track record of resistance to Ben Ali.
A doctor and the former president of the Tunisian human rights league, he was first jailed and then forced into exile until the fall of the dictator.
Marzouki, who founded the CPR in 2001, is a gifted speaker and respected by many as a man of integrity.
He has defended himself against those who denounce his willingness to negotiate with Ennahda by stressing the moderate nature of the movement, while insisting that he will not compromise on basic human rights.
But some have also reproached what they see as his unseemly haste in announcing his decision to announce his run for the presidency just three days after Ben Ali had fled.
Ben Jaafar, 71, heads the leftist Ettakatol (Forum) party. One colleague has described him as as a hand of steel inside a velvet glove.
While his gift for dialogue and affable manner helped keep him out of Ben Ali's jails, when it came to his principles, he never gave an inch, the colleague said.
With his polite manner and cutting wit he knows how to cut his adversaries down to size, one veteran of the Tunis diplomatic scene said. "We saw him do it under Ali," the diplomat added.
The task of the new constituent assembly is to draw up a new constitution and appoint a caretaker government until the country calls a general election.
Abdelwaheb Matar, who took part in the negotiations on behalf of the CPR, told AFP the CRP still had to be approved Tuesday's inaugural meeting of the constituent assembly.
A senior Ettakatol official, who also confirmed the deal, added that the three parties were still in talks to determine who would get which ministerial posts in the new interim government.
Ennahda leader Ghannouchi meanwhile, on a three-visit to Algeria, already appeared to be enjoying a treatment that reflected his new-found status, according to diplomatic sources and media reports.
Ghannouchi was accompanied by the president of the Algerian Senate, Abdelkader Bensaleh, Le Soir d'Algerie reported -- a treatment normally reserved for a head of state, it noted.