Tunisia's trade union body announced mass protests on Sunday to force out the government, accusing the Islamist-led coalition of delaying crisis talks on the country's political future.
The powerful UGTT union had been acting as mediator between the government and the secularist opposition, but said talks stalled on Saturday due to the ruling Ennahda party's refusal to announce its immediate resignation.
The UGTT said it would stage protests across the country and then a huge rally in the capital to force the government out.
"All options remain possible" UGTT spokesman Sami Tahri said, referring to the possibility of a general strike. Another official hinted that a change in heart from the government could avert mass protests.
"The door is still open for those who refuse this initiative," UGTT official Hussein Abassi told reporters. "We can still wait for a few hours or days, but we cannot wait for long."
The UGTT has been pushing both sides to accept a proposal for three weeks of talks after which Ennahda would hand over to a caretaker administration until elections were held.
Tunisia, where the ouster of President Zine al-Abidine Ben Ali in 2011 triggered the wave of "Arab Spring" revolts, had been considered as one of the more successful among the region's fledgling democracies.
But unrest broke out after the assassination of an opposition figure in July. The opposition accused the moderate Islamist party Ennahda of tolerating Islamist militants and demanded it step down.
Whereas in Egypt military power decided the Islamist government's fate, in Tunisia the economic muscle of the 800,000 member union may prove decisive.
A single day of strikes last July cost the country hundreds millions of dollars and sent its currency to a historic low against the dollar.
The Tunisian army may have played a role in Ben Ali's overthrow by refusing to shoot demonstrators. But unlike the Egyptian military, which also helped protesters to topple autocrat Hosni Mubarak in 2011, it remains politically weak.
It has few strings to pull and, unlike the Egyptian military, little economic privilege to protect.
The protests will be the first show of strength by UGTT since it started mediation more than a month ago.