Premier Silvio Berlusconi and Senate and House Speakers Renato Schifani and Gianfranco Fini will attend solemn funerals on Friday for many of the 281 victims of Monday's earthquake in Italy's central Abruzzo region.
It is still uncertain whether President Giorgio Napolitano, who visited the devastated areas on Thursday, will also take part, government sources said.
Centre-left opposition leader Dario Franceschini will also attend.
Officials in L'Aquila said that a brief Islamic rite would be held at the end of the Catholic commemoration in honour of six Muslim victims.
Government sources said the cabinet had decided to commemorate the victims with a solemn funeral in a sign of nationwide mourning for the 281 victims.
State funerals, the sources said, are instead held for top-ranking officials, public personalities and victims of terrorism or organised crime.
The ceremony will be broadcast live by state-run television RAI's first channel, and private broadcasters La7, Sky's TG24 and Mediaset's Canale 5.
A number of business and artisans' associations and nationwide supermarket chains announced they would suspend activity for the duration of the ceremony.