* Opposition agrees to discuss transition plan
* Plan envisages caretaker administration, elections
* Government had agreed to talks despite reservations
* Weeks of unrest had threatened move towards democracy
By Tarek Amara
TUNIS, Sept 20 (Reuters) - Tunisia's opposition coalition agreed on Friday to start direct talks with ruling Islamists on a transition plan under which the government would step down and make way for a caretaker administration and new elections.
The agreement follows weeks of unrest that erupted after the assassination of an opposition figure in July.
The secular opposition accused the moderate Islamist ruling party, Ennahda, of tolerating the Islamist militants it blamed for the killing, the second in six months, and staged large protests, demanding the government step down immediately.
Issam Chebbi, a senior official in the Salvation Front, told Reuters the opposition decided to accept "without any conditions" the initiative proposed by the powerful UGTT labour movement which has been mediating in the dispute.
Ennahda had already accepted the negotiation plan after expressing some initial reservations it said would be discussed during talks.
A formal announcement by the UGTT about the agreement is expected on Saturday. It should lead to the start of a three-week negotiation period after which the Ennahda-led government will step down.
The two sides will discuss a timetable for new elections, the composition of the caretaker government and other guarantees for the country's transition to full democracy.
Tunisia, where the overthrow of President Zine al-Abidine Ben Ali in 2011 was the first "Arab Spring" revolt, has been caught in deadlock for weeks, delaying a political transition that had been seen as one of the more successful among the region's nascent democracies.