Italian President Giorgio Napolitano is holding crisis talks with political leaders following the resignation of Prime Minister Romano Prodi.
Mr Prodi stepped down after being defeated in a vote of confidence in the upper house of parliament, the Senate.
The president is said to favour an interim government to push through much-needed electoral reforms.
But opposition leader Silvio Berlusconi is calling for snap elections, which would favour his centre-right party.
Mr Napolitano began the series of talks by meeting Senate speaker Franco Marini.
Mr Marini, 74, who heads a small centrist party, is seen as a possible interim prime minister who could muster cross-party support to change electoral laws.
The consultations - with parliament speakers, party leaders, whips and former presidents - will last until Tuesday, a statement by the president's office said.
The BBC's Christian Fraser says there is widespread agreement among several senior senators - even among Mr Prodi's opponents - that the country needs new electoral laws.
Under the current system rushed in by Mr Berlusconi during his time as prime minister, smaller parties with only a handful of seats hold the balance of power in parliament.
This is what caused the current crisis. The loss of the small, centrist Udeur party's three seats in the upper house left Mr Prodi without a majority and requiring the support of several unelected life senators.
In the Senate vote, Mr Prodi's government fell four votes short of the 160 it needed to survive, with 161 senators voting against and one abstention.
Opposition senators celebrated Mr Prodi's defeat with champagne
Mr Prodi, who led his centre-left coalition for 20 months, has been asked to continue as prime minister in a caretaker capacity until the president decides to call for elections or the formation of a new government.
Our correspondent says Mr Berlusconi is unlikely to pass up the opportunity to press for snap elections given that his Forza Italia party is leading the polls.
Members of his coalition cracked open champagne to celebrate Mr Prodi's defeat and the flamboyant former prime minister announced a surprise party at his house in Rome.
"We will say what we want to do in the first 100 days of our government," said Mr Berlusconi.