Tunisia will hold an election on July 24th to choose a "constituent council" that will rewrite the constitution and chart the country's transition after the ousting of its veteran leader, the interim president said.
In a televised speech late today, interim president Fouad Mebazza said he and the current caretaker government would stay in power until the election was held.
"We are proclaiming today that we are entering a new era ... and a new political system which definitively breaks with the ousted regime," Mr Mebazza said. A source close to the president's office told Reuters that, once elected, the constituent council could either appoint a new government or ask the current executive to carry on until presidential and parliamentary elections were held.
Tunisia has struggled to restore stability since mass protests ousted veteran president Zine al-Abidine Ben Ali on January 14th after 23 years in power.
Interim authorites initially promised to hold a presidential election by mid-July but persistent street unrest and a wave of resignations from the caretaker government threatened to derail the fragile transition.
Analysts said the president's announcement laid out a road map for the transition and could relieve some pressure on the interim government, but it was not clear if it would be enough for it to survive.
"I think it's an important step towards reconciliation," said Slaheddin Jourchi, a political analyst in Tunis. "At least now the interim government has a clearer agenda, an expiry date on its mandate," he said.
Changing the constitution is regarded as a vital step towards creating a proper multi-party system and paving the way for democratic elections.
That may take some time - Mr Jourchi estimated it would be up to two years before a presidential election is called.
Also it was not immediately clear what would happen to parliament, where Ben Ali's old guard still holds sway.
The Tunisian revolution has provided the inspiration for uprisings in other parts of the Arab world.
But North Africa's most developed state has suffered outbreaks of violence, and huge protests have put pressure on the interim government, leading some commentators to predict the military may step in to take over the transition.
Security forces killed five protesters on Saturday, and six high-profile members of the caretaker executive government have stepped down since Sunday as demonstrators vented their anger at the slow pace of change since Mr Ben Ali's departure.