"My role is to bring my country out of this temporary phase and even if I am nominated, I will refuse it and leave politics," the BBC reported Ghannouchi said Friday in an interview on Tunisian television, although no election date was announced.
Tunisia has been wracked by violent protests since December, heightened when President Zine el-Abidine Ben Ali fled to Saudi Arabia this month.
Many Tunisians consider Ghannouchi to be a "leftover" of Ben Ali's rule.
Ghannouchi said assets held offshore by Ben Ali had been frozen and would be returned to the state, but didn't elaborate, The Daily Telegraph said.
Ben Ali's party known as RCD folded Thursday and its Cabinet members all resigned, CNN said.
Three days of national mourning began Friday for those who died in the protests, the British newspaper said. Estimates of the number of dead have ranged from 78 to 100.
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