"President Aoun responded to the wishes of (caretaker) prime minister Saad Hariri to postpone parliamentary consultations until Thursday December 19," the presidency announced on Twitter.
The government stepped down on October 29 in the face of unprecedented nationwide protests.
The names of various potential candidates to replace Hariri have been circulated in recent weeks but bitterly divided political parties in the multi-confessional country have failed to agree on a new premier.
Earlier this month the Sunni Muslim establishment threw its support behind Hariri returning, further angering protesters who have demanded a cabinet of independent experts.
Demonstrations on Sunday in Beirut began peacefully with protesters waving Lebanese flags and chanting "Hariri will not return".
Clashes erupted later for the second night in a row near parliament, with demonstrators throwing water bottles and firecrackers at the security forces who responded with tear gas and water cannon, an AFP photographer said.
Saturday evening had seen dozens of people hurt when security forces used tear gas and rubber bullets to disperse demonstrators who tried to breach metal barricades near the legislature.
The international community has urged a new cabinet to be formed swiftly to implement key economic reforms and unlock international aid as Lebanon's debt-burdened economy slides towards collapse.