The United Nations gathered Libya's rival factions for talks in Geneva Wednesday, amid warnings they could be the last chance to halt intensifying fighting for the country's main cities and oil wealth.
The North African nation has been gripped by deepening conflict since the overthrow of dictator Moamer Kadhafi in a NATO-backed uprising in 2011, with rival governments and powerful militias battling for control.
It has taken the United Nations months to get the opposing sides back to the negotiating table after a single round of talks in September.
But analysts warned that the Geneva negotiations between Libya's political rivals were unlikely to have any impact on the ground unless the leaders of the warring armed groups become directly involved.
The talks will be overseen by the UN special envoy for Libya Bernardino Leon who has been shuttling between the parties to the conflict for months.
He was to hold a 1330 GMT news conference ahead of the opening.
The talks are aimed at reaching agreement on the formation of a unity government to replace the rival administrations whose battle for power has left hundreds dead over the past six months.
They also seek to "put in place the necessary security arrangements for bringing about a total cessation of armed hostilities" and "secure a phased withdrawal of all armed groups from all major towns and cities."
The internationally recognised government has been based in the remote east since an Islamist-backed militia alliance seized Tripoli in August and set up its own administration.
The alliance known as Fajr Libya (Libya Dawn) also holds third city Misrata. It launched a bloody offensive in December to seize control of key oil terminals but was repelled by the army.
Most countries pulled out their diplomats from Tripoli after the city was taken by Libya Dawn.
In a mark of the difficulties the United Nations has faced in convening the Geneva talks at all, the UN mission acknowledged late on Tuesday that the attendance of several key participants had yet to be confirmed.
The European Union, which has watched with mounting concern as jihadist groups have taken advantage of the conflict to establish a foothold just across the Mediterranean, called on all sides to take part.
"This is an opportunity the Libyans cannot afford to miss," the EU's foreign policy chief Federica Mogherini said on the eve of the talks.
"I want to praise both sides participating and encourage all those in Libya that have not yet decided on participation... to do so".
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Mogherini warned on Saturday that the Geneva process "represents a last chance which must be seized".
- 'Wrong actors' -
The confirmed participants include supporters of the recognised government and some backers of the rival Tripoli administration.
But only politicians have been invited, not the commanders of the warring armies, and analysts warned that without their participation the negotiations were unlikely to bring about an end to the fighting.
"The dialogue will fail because the UN has not chosen the right actors," said political analyst Mohammed al-Ferjani.
"The participants are politicians and have no presence or influence on the ground."
Libya Dawn leaders have not been invited to Geneva, nor have representatives of the most powerful commander on the recognised government side, Khalifa Haftar.
A former Kadhafi general turned 2011 rebel leader, Haftar established a militia in eastern Libya that was initially disavowed by recognised Prime Minister Abullah al-Thani before being embraced after his flight from the capital.
Haftar has led repeated offensives against Islamist militias in Libya's second city Benghazi since May, which have succeeded in wresting back control of large areas.
Those militias are led by the Ansar al-Sharia group, blacklisted by the United Nations for links to Al-Qaeda, and Thani has repeatedly appealed to the international community for weapons to press the campaign.
The heavy fighting for Benghazi, a city of about one million people, has killed hundreds of civilians, drawing repeated calls from the United Nations and Western governments for a ceasefire.
The Islamic State group that has seized large areas in Iraq and Syria is also thought to have gained a foothold in eastern Libya, and recently claimed to have executed two Tunisian journalists there.