After meeting Napolitano, Franco Marini, Italy's Senate speaker, said: "I know well that this is not an easy enterprise, in fact it's a hard one."
Marini said he would act quickly with political talks scheduled to start on Thursday and last a few days.
If he fails, the only apparent option would be an immediate general election just two years after the last one.
The next scheduled date is 2011.
A centrist and a veteran of Italian politics, 74-year-old Marini is a former leader of one of Italy's largest unions.
As senate speaker he holds the country's highest-ranking position and will need all his widely recognised mediating skills to succeed.
Berlusconi, riding high in opionion polls, says early elections are the only way out of the crisis, and has rejected any other options, including that of an interim government.
Speaking on Wednesday, he said: "There is no room for dialogue on the electoral law. This country needs many things, but not to waste time."
Already the longest ever serving Italian postwar premier with a 2001 to 2006 period in office, Berlusconi is eager for a return to power.
Gianfranco Fini of the right-wing National Alliance predicted Marini would fail, while the Northern League announced that it would not even take part in the talks.
|Berlusconi says early elections are the |
only way out of the crisis [AFP]
Both are coalition partners of Berlusconi.
The centre-left finds itself in the opposite situation.
Shattered by Prodi's resignation after less than two years in office, it favours an interim government to enact reforms and delay the vote.
Walter Veltroni, the likely centre-left candidate for premier at the next vote, has long demanded a reform of the election law, widely blamed for fostering Italy's political instability.
He insists that electoral reform can be passed in a few months in the interest of the whole country.
The current proportional-representation system was passed during the waning days of Berlusconi's government but was criticized then even by some of its proponents.
It is seen as giving disproportionate weight to small parties, thus fostering instability.
Prodi resigned last Thursday after he lost a confidence vote in the senate, due to defections by some allies.