Tunisia's main parties rejected a proposal on Thursday by the moderate Islamist party Ennahda to name a prime minister from its own ranks following its victory in last month's parliamentary elections.
Any political deadlock resulting from the sharply fragmented parliament would complicate Tunisia's efforts to address chronic economic problems including a large public debt and 15% unemployment.
Ennahda will be the largest party in Tunisia's new parliament but with only 52 of 217 seats, forcing it to compromise to form a Cabinet. Ennahda said it had decided that one of its leaders should be prime minister because Tunisians had given it the responsibility to implement its electoral programs.
But the proposal was not accepted by potential coalition partners Attayar with 22 seats, Achaab's Movement with 16 seats and Prime Minister Youssef Chahed's Tahya Tounes party, with 14.
Only the Conservative Karama coalition, with 21 seats, agreed.
In a second meeting with Ennahda on Thursday, Attayar said it would not accept a prime minister from Ennahda, and asked for the portfolios of justice, interior and administrative reform in the new government.
Gazi Chaouachi, a senior leader in Attayar, said Tunisia needed a consensus prime minister from outside Ennahda, with an economic background to help save the ailing economy.
Thaya Tounes also said it would not join a Cabinet led by Ennahda and called for a government of "national interest" focused on urgent economic reforms.
Ennahda has excluded two parties from talks: Heart of Tunisia, which holds 38 seats and is led by the media magnate Nabil Karoui, and the Free Constitutional Party led by Abir Moussa, with 17 seats, which opposes the Islamists.
Ennahda is expected to reveal its choice for prime minister by the end of this week or early next week. If it goes ahead with its decision to name a politician from its own ranks, possible choices include its leader Rached Ghannouchi, or Zied Ladhari, the minister of investment who resigned on Thursday.
If Ennahda cannot form a government within two months, the president can ask another group to try. If that fails and the deadlock persists, there will be another election.