ROME (AFP) - Italian lawmakers meet on Thursday to begin voting on a new president in a key step that could end a two-month impasse between political parties that has blocked the formation of a new government.

A joint session of both chambers of parliament meeting together with regional representatives is called on to elect a successor to President Giorgio Napolitano, who failed to clinch an agreement between bickering political forces.

The election could take a single day or several or even weeks, with a two-thirds majority required in the first three rounds of voting and a simple majority thereafter.

"We are walking on thin ice," said Mr Stefano Folli, columnist for Il Sole 24 Ore daily, warning that the political system is "too worn out and frayed to resist the pressure of a conflict for the presidency over several days".

No single party or coalition holds a majority, meaning that there will have to be some kind of compromise - which analysts hope could be the basis for a long-delayed deal on a government for the eurozone's third-largest economy.

The main centre-left coalition won a general election on February 24-25 but only by a whisker and it failed to get enough votes for an overall majority in parliament.

Coalition leader Pier Luigi Bersani has tried to woo lawmakers from a new anti-establishment party, the Five Star Movement, but has been rebuffed.

Mr Bersani has ruled out the most obvious alternative - a grand coalition with Silvio Berlusconi's centre-right - which would prove hugely controversial among leftists fiercely opposed to the scandal-tainted billionaire tycoon.

The question of whether or not to strike a deal with Berlusconi has threatened to split Mr Bersani's Democratic Party. The issue of two ongoing trials pending against Berlusconi - one for tax fraud and the other for allegedly having sex with an underage prostitute - is also looming.

Mr Berlusconi has said there should be new elections if there is no cross-party deal with Mr Bersani and opinion polls indicate he would win, although they show he would still fail to get a majority.

The 87-year-old Napolitano was constitutionally prevented from dissolving parliament and calling new elections because he was in the last months of his seven-year mandate but his successor will have full powers to do so.

While the presidency in Italy is a mostly ceremonial post, it takes on critical importance during times of political crisis, as shown by Napolitano's manoeuvring to put Mario Monti in power when Berlusconi was ousted in 2011.

Some analysts say elections could be held as soon as late June - a prospect that could have worrying consequences for Italy on the financial markets, which have remained relatively muted.

Big business and trade union leaders have urged politicians to strike an agreement, warning that there is no time to lose as Italy endures its worst economic recession since the post-war period.

Mr Giorgio Squinzi, head of the main employers' association Confindustria, has said the protracted political crisis has already cost the economy around 1.0 per cent in gross domestic product (GDP).

The Catholic Church, which remains influential in Italy, has also upped the pressure.

Cardinal Angelo Bagnasco, head of the Italian bishops' conference, on Tuesday said: "The political world should stop its delays".

"People have had enough," the cardinal said after celebrating mass at a crisis-hit shipyard in the port of Genoa in northern Italy.

An array of names has been making the rounds of Italian newspapers in recent days over who could be the next president - a mediatic build-up not dissimilar to the conclave of cardinals that elected Pope Francis last month.

Two former prime ministers are frequently cited as possible candidates - Giuliano Amato and Romano Prodi - but there are also rank outsiders like former European commissioner Emma Bonino, who would be the first female president.

The Five Star Movement held an online poll among its members which identified investigative journalist Milena Gabanelli, editor of the news programme "Report" on public television, as its candidate.

Ms Gabanelli is seen as having virtually no chance.

Mr Giovanni Guzzetta, a constitutional expert at Tor Vergata university in Rome, said: "Once the president is elected, we will understand who is going to be in the government."