Turkish Prime Minister Ahmet Davutoglu is due to begin coalition talks on Monday with the second-placed CHP party after last month's elections where his ruling party lost its overall majority.
Davutoglu's ruling Justice and Development Party (AKP) failed to secure enough votes in the June 7 elections to form a government alone, for the first time since it came to power in 2002.
The AKP has 258 seats in the new parliament, the Republican People's Party (CHP) 132, and the Nationalist Movement Party (MHP) and pro-Kurdish People's Democratic Party (HDP) hold 80 apiece.
Davutoglu will meet this week with each of the three other parties in parliament, but no agreement is expected this week during the Eid feast marking the end of holy Muslim month of Ramadan.
On Monday, he will hold talks with CHP leader Kemal Kilicdaroglu at 1100 GMT at the CHP headquarters in the capital Ankara.
A coalition between the AKP and the nationalist MHP is seen by far the most likely option because both parties share a core conservative voter base in the centre of the country.
Both AKP and HDP have excluded joining forces.
If efforts to form a coalition within the constitutional limit of 45 days are unsuccessful, President Recep Tayyip Erdogan can call snap elections within 45 days.
Erdogan's authority is one of the tricky issues in coalition negotiations because opposition parties are contesting his broad presidential powers.
Davutoglu said discussing Erdogan's authority was out of the question.
"Bringing our president's legitimacy or prestige into question right now would sabotage coalition talks from the first," Davutoglu told the Hurriyet newspaper.
The June election was a blow not only to the AKP's authority but also to Erdogan, who had been hoping the new parliament would agree on a new constitution to increase his powers.