BEIRUT (Reuters) - Rival Lebanese leaders are struggling to agree on a successor for the president whose term ends this week, a step vital to defusing a prolonged crisis, political sources said on Sunday.

Lebanon faces the prospects of two parallel governments and maybe bloodshed if parliament's Western-backed majority and the Hezbollah-led opposition fail to elect on Wednesday a successor to President Emile Lahoud, whose term ends on Friday.
The deadlock, the climax of a year-old political crisis that has paralyzed the country, has prompted international efforts led by France to nudge the Lebanese leaders towards agreement.
Majority leader Saad al-Hariri and parliamentary speaker Nabih Berri, also an opposition leader, discussed on Saturday a list of candidates presented to them by Maronite Christian Patriarch Nasrallah Sfeir.
""The atmosphere of discussions was positive and boosted the chances of consensus on the presidency,"" a joint statement said.
But political sources said the talks did not lead to agreement and expected both men to intensify their meetings in the next few days.
The majority coalition has said it would elect a president on its own if there was no deal, while the opposition have threatened to set up a second government.
The political conflict is Lebanon's worst internal crisis since the 1975-1990 civil war.
At former colonial power France's prodding, the head of the Maronite church had given a list of six candidates to Hariri and Berri to choose a new president from.
The president must be a Maronite in line with the country's sectarian power-sharing system.
Political sources say the list includes MP Boutros Harb and former MP Nassib Lahoud from the governing coalition and the opposition's Christian leader Michel Aoun.
But the consensus figure is expected to be one of three moderate candidates named by Sfeir. They are parliamentarian Robert Ghanem, former central bank governor Michel Khoury and former minister Michel Edde.
Hariri and Berri met hours after Italy's Foreign Minister Massimo D'Alema visited Beirut. D'Alema said the leaders could agree on a new president but warned ""everything could still go wrong"".
D'Alema said a stumbling block was Aoun's insistence he should fill the post. He urged the opposition leader to show more flexibility.
The Italian minister said he might visit Lebanon again with his French and Spanish counterparts, who had visited Beirut earlier this month.
Aoun, a former general, is leader of the biggest Christian bloc in parliament and part of the opposition, which has been locked in a power struggle with the Western-backed governing coalition for more than a year.
The candidate will be Lebanon's first new president since Syria pulled its troops out of Lebanon in 2005.