Center-left leader Matteo Renzi was set to be nominated as Italy's youngest prime minister in a matter of days after a party coup forced Enrico Letta to resign as premier of the euro zone state struggling to pull out of recession.
Letta bowed out on Friday after his Democratic Party (PD) forced him to step aside and make way for Renzi, 39, who is promising bold economic reforms and a government than can survive until 2018.
President Giorgio Napolitano was likely to ask Renzi, the current mayor of Florence, to put together a government on Monday, a PD source told Reuters.
The president completed consultations with parties on Saturday evening without announcing his preferred candidate.
"It was an interesting and richly stimulating day in which I received many suggestions that I must pass on to the person who I ask to form a government," Napolitano told reporters after a full day of talks.
Renzi, whose PD is the largest party in parliament, would become the youngest leader in Italy's 163-year history as a united country, younger even - by two months - than Fascist dictator Benito Mussolini was when he took over in 1922.
But before he can stake his claim on history and attempt to install Italy's 65th government since World War Two, he must overcome institutional rituals and much political wheeling-and-dealing, a process likely to take several days.
After receiving a mandate from the president, he will have to strike an accord with the small New Centre Right (NCD) party, whose support the PD needs to command a majority in the parliament of the euro zone's third-largest economy.
The party, which split from scandal-plagued tycoon and ex-premier Silvio Berlusconi last year, said it was ready to work with the center-left on forming a new government after meeting Napolitano.
But it made it clear it would demand guarantees in areas from tax and jobs to family policy, meaning a new government may not be in place until next week.
"We have very clear and concrete ideas on what the policy platform must be. If the ambition of the new government is great, then we cannot do things in a rush," said NCD leader Angelino Alfano, who saw no accord in "less than 48 hours".
(Read more: 'Demolition Man' Renzi's next fight: Berlusconi)