* Negotiations with coalition partners likely to last days
* New government may be sworn in this week
Italian centre-left leader Matteo Renzi said on Monday he would begin talks to form a new government in the next 24 hours, and expected to lay out a programme of reforms to be completed within the next few months.
Renzi needs to seal a formal coalition deal with the small centre-right NCD party to secure a majority and to name his cabinet before seeking a formal vote of confidence in parliament, probably later this week.
He has promised a radical programme of action to lift Italy out of its most serious economic slump since World War Two but will have to deal with the same unwieldy coalition which failed to pass major reforms under its previous leader.
"In this difficult situation, I will bring all the energy and commitment I am capable of," he told reporters after a 90-minute meeting with President Giorgio Napolitano when he was given a mandate to form a new government.
"The sense of urgency is extraordinarily delicate and important but it's also true that, given the time horizon we have set of a full parliamentary term, we'll need a few days before formally accepting the mandate," he said.
The 39-year-old mayor of Florence has been expected to take over since he engineered the removal of his party rival Enrico Letta as prime minister at a meeting of the Democratic Party leadership last week, following growing impatience with the slow pace of economic reforms.
The euro zone's third largest economy is technically no longer in recession since it scraped back into growth in the fourth quarter of 2013. However, it remains profoundly marked by the crisis with a 2 trillion euro ($2.74 trillion) public debt, a rapidly crumbling industrial base and millions out of work.
Renzi said he expected to lay out full reforms to Italy's electoral law and political institutions by the end of February, to be followed by labour reforms in March, an overhaul of the public administration in April and a tax reform in May.
He made no comment on the likely makeup of his cabinet.