Rival Lebanese leaders made progress towards ending their political crisis on Sunday but disagreements over Hezbollah's weapons remained a major hurdle to a Qatari-mediated deal.

Qatar's emir, Sheikh Hamad bin Khalifa al-Thani, weighed in on the third day of talks, meeting members of the U.S.-backed ruling coalition and Hezbollah-led opposition to try to bridge differences.

Delegates said Sheikh Hamad brought together Prime Minister Fouad Siniora and Parliament Speaker Nabih Berri, a senior opposition leader, for the first time in 18 months as part of efforts to solve the crisis that has left Lebanon with no president and taken it close to civil war.

Delegates said the differences were slowly narrowing over the two key issues on the agenda -- a new election law and power-sharing in the government.

But talks may yet stumble over a demand from the governing coalition for clear guarantees that Hezbollah, which is backed by Iran and Syria, would not turn its guns on them again and that the fate of its arms would be debated in Lebanon soon.

Arab mediators clinched a deal on Thursday to end Lebanon's worst internal fighting since the 1975-1990 civil war, in which Hezbollah routed supporters of the U.S.-backed government and briefly seized parts of Beirut.

At least 81 people were killed in the violence, which exacerbated sectarian tensions between Shi'ites loyal to Hezbollah and Druze and Sunni followers of the ruling coalition.

The fate of Hezbollah's weapons is not on the agenda of the Doha talks but delegates said Arab mediators were consulting on the issue with regional power brokers including Iran and Saudi Arabia, which is a leading supporter of the ruling coalition.

"This issue is not under discussion and is not up for discussion on the table of dialogue in Doha," said Hezbollah MP Hussein Hajj Hassan.

Washington blames Syria and Iran for Hezbollah's offensive last week which forced the U.S-supported government to rescind two decisions that had triggered the escalation.

U.S. National Security Adviser Stephen Hadley said the Doha talks should aim to curb Hezbollah and bolster the government.

"This can lead to an end to the political stalemate, but only if it does not reward Hezbollah, and if it supports the elected government..." he said, adding that the talks were an opportunity to hold Hezbollah to account and "clip its wings."

DEFINING MOMENT

Notwithstanding the sensitive issue of Hezbollah's weapons, the talks appeared to make headway on Sunday.

A six-member committee created on Saturday to lay the framework for a new election law has made progress and was now working out the details of how to divide Beirut electorally.

"I think we have resolved 90 percent of the hurdles facing the new election law. We have some obstacles left regarding some electoral constituencies," said Amin Gemayel, a former president and member of the ruling coalition.

"Hopefully, by evening we will have published a joint vision. We have to reach a solution in the end."

Qatari Prime Minister Sheikh Hamad bin Jassim bin Jabr al-Thani had yet to win final approval on the shape of a new government but had made several proposals, including one to split seats three ways equally among rivals, delegates said.

Secretary General Amr Moussa told Free Lebanon radio he expected "today to be a decisive day" at the Qatar talks that seek to end the 18-month political stalemate and facilitate the election of a president after a 6-month vacuum.

The Hezbollah-led opposition wants more say in a cabinet controlled by factions opposed to Syrian influence in Lebanon.

The ruling coalition's refusal to yield to the demand for an effective veto power in the cabinet triggered the resignation of all Shi'ite ministers in November 2006, crippling a political system built around the delicate sectarian balance.

Election laws have always been a sensitive subject in Lebanon, a patchwork of religious sects where redrawing constituencies can have a dramatic impact on voting results.