The coalition's approval of the plan may open up an immediate dialogue with the its secular opponents and end the unrest that erupted after the assassination of an opposition figure in July.
"Our response to the initiative of the union was positive as a platform for dialogue with the political parties," said Ameur Larayedh, a senior official in the moderate Islamist ruling party Ennahda.
Tunisia, where the overthrow of President Zine al-Abidine Ben Ali in 2011 has been in crisis for weeks, souring a political transition that had been seen as one of the more successful among the region's nascent democracies.
Stepping in to mediate, the UGTT labor union proposed a timetable on Tuesday for the government to step down in three weeks and make way for a caretaker administration to oversee elections.
"We have some reservations, but we are ready to discuss these points within the dialogue, which we expect to begin next Tuesday probably," Larayedh told Reuters.
Emad Daymi, head of the CPR party, one of Ennahda's junior coalition partners, also expressed support for the plan.
The opposition alliance, which includes some Ben Ali-era figures, is still studying the proposal, officials said.