Italy's Parliament failed to elect the country's new president Tuesday in a second round of voting, further delaying center-left leader Romano Prodi's bid to get a mandate to form a government.

More than 700 of the nearly 1,000 electors comprising members of Parliament and regional representatives submitted blank ballots, making it impossible for any one candidate to obtain the necessary two-thirds of votes.

Prodi's Union coalition has been pushing for former Communist Giorgio Napolitano, a widely respected senator-for-life, to assume the presidency. But members of the conservative coalition of outgoing Premier Silvio Berlusconi said earlier in the day that they were not ready to yield.

Casting blank ballots was seen as a delaying tactic while the two blocs pursued behind-the-scenes negotiations.

CountryWatch: Italy

Former Reforms Minister Roberto Calderoli told reporters the conservatives would not vote for Napolitano, and would submit blank ballots in the second round. Berlusconi told reporters his coalition would submit blank ballots in the third and fourth rounds of voting as well.

A third round began later Tuesday and was expected to last for a few hours.

If that fails to yield a president, a fourth round — the first that would only require a winner to earn more than half the votes rather than two-thirds — would be held on Wednesday.

Prodi's Union also had said it would deliver blank votes in the second round of balloting, saying it would use the tactic to force Berlusconi's forces to back Napolitano, Italian news agencies reported.

"This signifies a strong support for Napolitano's candidacy," Prodi told reporters, speaking a few hours before the second vote. "Let's hope for an agreement in the not too distant future."

Prodi later said his coalition would submit blank votes in the third round as well, but planned to go with Napolitano for the fourth round on Wednesday.

A total of 724 people submitted blank ballots in Tuesday's vote. Umberto Bossi, the leader of the Northern League — the often xenophobic, anti-immigrant party within Berlusconi's coalition — earned the most votes of any one name, with 38 votes.

Prodi's coalition has a small majority in the Chamber and a very slender margin in the Senate, meaning that without the opposition's help, it lacks the votes on its own to elect its choice before the margin required drops to a majority starting with the fourth round of voting.

President Carlo Azeglio Ciampi, whose seven-year term expires later this month, was elected in 1999 on the first ballot. But 16 rounds of voting and 13 days were necessary to elect his predecessor.