ROME – Italy’s parliament appeared headed yesterday toward a split between the conservative coalition headed by Premier Silvio Berlusconi and one led by his center-left challenger – an election result 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% of the vote compared to 49.7% won by Mr. Berlusconi’s conservatives. The winning coalition is automatically awarded 55% of the seats, according to a new electoral law.

According to the results, Mr. Berlusconi’s conservative allies 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 Mr. Prodi, speaking to his supporters.

“I am grateful to all of you because it has been a very difficult battle,” Mr. Prodi said.”Until the very end we were left in suspense, but in the end victory has arrived.”

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

During his tenure, Mr. Berlusconi, a flamboyant billionaire, had strongly supported President Bush over Iraq despite fierce Italian opposition to the war. Mr. 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 Mr. Berlusconi announced that Italy’s troops there would be withdrawn by year’s end.

For hours after the vote ended yesterday, 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%.

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.

Even with a slim majority in parliament’s houses, a coalition would officially win. But it would find it extremely difficult to pass legislation.

If parliament is split between the two coalitions, the president 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.

Mr. Berlusconi, a 69-year-old press and broadcasting mogul, was battling to capture his third premiership 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.

Mr. Prodi, 66, 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. Mr. Berlusconi failed to jump-start a flat economy during his tenure, but promised to abolish a homeowner’s property tax. Mr. Prodi said he would revive an inheritance tax abolished by Mr. 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.