A deal between Tunisia's main parties to end a protracted political crisis was thrown into doubt Friday after the agreed choice of interim premier had second thoughts about taking the job.
Mustapha Filali, who is 92 and served as agriculture minister under Tunisia's founding president Habib Bourguiba, ruled himself out after earlier indicating he was ready to accept the job.
Filali would be the oldest person ever appointed as prime minister, according to Guinness World Records.
The continuing efforts being made to secure a change of heart were a mark of the difficulty the Islamist-led government and the mainly secular opposition have had in coming up with a mutually acceptable nominee.
Fethi Ayadi, a leader of the ruling Islamist party Ennahda, said the negotiators were still trying to persuade Filali to agree to head the planned new government of technocrats.
"We have communicated with Mr Filali to convince him to take on this responsibility. If he refuses, we will respect his opinion," Ayadi told Shems FM radio.
The ruling Islamists and the opposition have been unable to agree on a premier since hard-won negotiations opened on October 25 to form a government of independents, draft a much-delayed constitution and prepare for elections as part of efforts to end the political impasse.
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"I have not proposed myself as a candidate, it is they who have proposed me," Filali told Mosaique FM radio.
"I will not accept this mission... I reject it because of my age, and because of the scope of the responsibilities and problems."
Houcine Abassi, a mediator from the powerful UGTT union confederation, announced on Thursday that a compromise had been reached on the choice of prime minister following a fresh round of talks.
Abassi said the contents of the long-awaited agreement would be announced at a meeting on Friday, but no time or place has been given for the announcement.
The mediators to the political crisis, which was sparked by the killing of opposition MP Mohammed Brahmi by suspected hardline Islamists in July, have given the political parties until Saturday to agree on an interim premier, threatening otherwise to announce the failure of negotiations.
Since Brahmi's death, the second political assassination of its kind in Tunisia this year, secular opposition parties have repeatedly called for Ennahda's resignation, amid heightened mistrust between the political factions that has overshadowed the crisis talks.
The political deadlock gripping the country, along with accusations that the Islamist-led government has failed to improve living standards or prevent a string of attacks by militants, is fuelling discontent, three years after the uprising that toppled Zine El Abidine Ben Ali.
According to Guinness World Records, the oldest person ever to take up the post of prime minister is currently King Abdullah of Saudi Arabia, who was born in 1924 and became both king and premier when he ascended the throne on August 1, 2005.