Italy's parliament headed toward an unprecedented split on Tuesday between Premier Silvio Berlusconi's conservative coalition and one led by his center-left rival — the result of a national vote that could stall the formation of a new government.

Final results in the two-day vote ending Monday showed Romano Prodi's center-left coalition winning control in the lower house of parliament, with 49.8 percent of the vote compared to 49.7 won by Berlusconi's conservatives. The winning coalition is automatically awarded 55 percent of the seats.

According to the results, Berlusconi's center-right coalition held a one-seat lead in the Senate, although six seats elected abroad were still to be counted.

"We have won, and now we have to start working to implement our program and unify the country," said a jubilant Prodi, speaking to his supporters. "Until the very end we were left in suspense, but in the end victory has arrived."

Berlusconi's spokesman contested the victory claim, and Prodi's allies conceded after his announcement that results in the Senate were still not complete.

During his tenure as premier, Berlusconi, a flamboyant billionaire, had strongly supported President Bush over Iraq despite fierce Italian opposition to the war. Prodi, an economist, said he would bring troops home as soon as possible, security conditions permitting. But the issue was largely deflated before the campaign began, when Berlusconi announced that Italy's troops there would be withdrawn by year's end.

For hours after the vote ended Monday, projections and returns swung dramatically back and forth between the two, and without the vote from abroad, the election's outcome was still unclear. Voter turnout was about 84 percent.

The Senate and lower chamber of parliament have equal powers, and any coalition would have to control both in order to form a government. Both center-left and center-right leaders have said if neither side controls both houses, new elections should be called.

"If there's a different majority between the Senate and the Chamber we need to go back to the polls," leading center-left lawmaker Luciano Violante said earlier in the day.

If parliament is split, President Carlo Azeglio Ciampi — a grandfatherly, highly respected economist and independent from partisan politics — could try to name a government of technocrats at least until another election. He could also seek to fashion a coalition of left and right, but considering the bitter divisions among Italy's political parties, that seemed unlikely.

There is no clear provision in the Italian constitution to deal with a split parliament, and there are no precedents.

Culture Minister Rocco Buttiglione and several other politicians said early Tuesday that both sides must pull together.

"We can't have new elections. We have to pass the budget law, elect a new president," Buttiglione said, suggesting that Italians might return to the polls in the fall.

Berlusconi, a 69-year-old media mogul and Italy's longest-serving premier since World War II, was battling to capture his third term with an often squabbling coalition of his Forza Italia party, the former neo-fascist National Alliance, pro-Vatican forces and the anti-immigrant Northern League.

The 66-year-old Prodi, a former premier, was making his comeback bid with a potentially unwieldy coalition of moderate Christian Democrats, Greens, liberals, former Communists and Communists.

Italians were mainly preoccupied by economic worries. Berlusconi failed to jump start a flat economy during his tenure, but promised to abolish a homeowner's property tax. Prodi said he would revive an inheritance tax abolished by Berlusconi, but only for the richest; he also promised to cut payroll taxes to try to spur hiring.

Still, the candidates seemed to hurl more insults at each other than comprehensive plans for turning around the economy.

The premier's critics have accused him of having used his coalition's comfortable majority in parliament to push through laws to protect his business interests. He founded a business empire that expanded to include Italy's main private TV networks, the Milan soccer team, as well as publishing, advertising and insurance interests.

Berlusconi, in turn, depicted Prodi as a front man for communists in a campaign to damage democracy.

Some analysts had suggested that Ciampi could give the mandate to form a new government to whoever won the lower house, whose members are elected by a wider number of people. Italians must be at least 25 to vote for the Senate, but 18 to vote for the lower house.

Franco Pavoncello, a political science professor at John Cabot University, said Ciampi's role would have to be that of mediator. But, he added, "If everything is blocked it's useless for him to waste his time."