UPDATE 1-Italian starts "impossible" job of forming govt

(Adds quote from centrist Udeur party, paragraphs 16-17)

By Robin Pomeroy

ROME Jan 31 (Reuters) - The head of Italy's Senate began seeking support on Thursday to form a new government, something he admitted was a near impossible task as opposition leader Silvio Berlusconi continued to insist on a snap election.

Franco Marini will meet political leaders and report back to President Giorgio Napolitano early next week to say if he has the numbers to create a new coalition. If not, Italy faces an election Berlusconi is sure will send him back to office.

With both Berlusconi and the leader of the second biggest centre-right party refusing to back an interim administration, Marini acknowledged his chances of garnering a cross-party consensus were slim.

"Impossible is a word that no one likes," Marini said. "I use a different word: difficult. It is very difficult."

"The path is narrow, but it might be that with good will and clarity in discussions I will have with political forces in this room, we might be able to find a chink of light, something that might be in the interest of our country," he told reporters.

The Italian president asked the 74-year-old upper house speaker to see whether he could form a temporary government whose main aim would be reforming an electoral law blamed for the Prodi administration's chronic instability.

That law was pushed through parliament by Berlusconi's government in the months before an April 2006 election which he narrowly lost to Prodi.

There is broad consensus that the system favours smaller parties, making it difficult for either of the main coalitions to win a clear-cut majority in the Senate.

Prodi's government was always on the verge of collapse as his two-seat upper house majority was at constant threat from dissent within his nine-party Catholics-to-communists bloc.

Berlusconi has acknowledged the current voting rules are flawed. But he says he could lead the centre right to a decisive victory even under the present system.

That was backed up by the latest opinion poll, for left-leaning L'Espresso weekly, which gave him a 16 percentage point lead over the centre left.

"MISSION IMPOSSIBLE"

"On paper it looks like a mission impossible," Italy's leading daily Corriere della Sera said of Marini's quest to form a government and stave off an early election.

Marini is not just up against Berlusconi and his allies, but also small parties who fear an electoral reform would reduce their weight in future coalitions or even exclude them from parliament.

The silver haired former trade unionist is a moderate figure and a Catholic respected by many, even on the right. He said he would seek a broad, solid consensus and not just eke out a few extra senators to prop up a new centre-left government.

His first consultation -- with rightwing senator Francesco Storace -- resulted in a predictable "no".

But so did his meeting with the small, Catholic Udeur party, a former Prodi ally whose defection triggered the centre-left government's downfall. The support of Catholic centrists appears crucial for Marini to be able to form a government.

"The sooner we go to the polls, the better," said Udeur leader Clemente Mastella, Prodi's former justice minister.

Berlusconi, Italy's richest man, considers himself already in an election race. The 71-year-old is beloved by many average Italians as they see him as a man of the people who made himself a billionaire in business.

Critics say he is a populist who used his previous terms in office to further his own legal and business interests. (Additional reporting by Paolo Biondi and Silvia Aloisi; Editing by Jon Boyle)