By Aidan Lewis and Ayman al-Warfalli
TUNIS/BENGHAZI, Libya (Reuters) - Libyan forces loyal to eastern commander Khalifa Haftar said on Monday they had tightened their control over four major oil ports, casting a Western-backed project to unite Libya and revive oil exports into deep uncertainty.
Haftar's forces met little resistance as they seized the terminals at Ras Lanuf, Es Sider, Zueitina and Brega in an operation launched on Sunday, displacing a rival armed faction aligned with the U.N.-backed Government of National Accord (GNA) in Tripoli.
The advance is the latest power struggle over the OPEC nation's energy assets, after the 2011 fall of Muammar Gaddafi and the chaos that followed left the North African country splintered into rival armed factions.
Haftar opposes the Tripoli government and has resisted its attempts to integrate his self-styled Libyan National Army (LNA) into unified armed forces. His seizure of the ports risks a response from powerful western brigades allied with the government and a deepening of regional divisions.
But Tripoli may seek a deal with Haftar, similar to the agreement it struck with the armed faction he has displaced, to restart the oil exports it needs to stave off a financial crisis that could paralyze government operations.
Conflict and political disputes have reduced Libya's oil output and exports to a fraction of the level seen before an uprising toppled late dictator Gaddafi five years ago.
In a statement signaling a willingness to get oil flowing, Haftar's LNA said late on Sunday it would secure the ports to "return operational responsibility to the National Oil Corporation with a guarantee of non-interference by armed forces in operational activities and exports".
The GNA's international backers said on Monday that LNA forces should withdraw immediately, that oil infrastructure had to remain under the control of the GNA, and that they would enforce a U.N. Security Council resolution against "illicit" oil exports.
Just a year ago, Libya had two rival governments, one in Tripoli and one in the east, each backed by competing factions of armed brigades and laying claims to the country's oil resources.
A unity deal brokered by the United Nations, signed by rival factions in December despite opposition from hardliners, was meant to end the divide. As a result of the agreement, the GNA arrived in Tripoli in March, backed by Western powers, to stabilize a country where lawlessness allowed Islamist militants and migrant smugglers to operate across swathes of territory.
Since then, however, some political and tribal leaders in the east have withheld their support, worried that the new government is a vehicle for opponents in the west. The LNA has strengthened its position, making military gains in and around Benghazi against Islamist-led opponents before taking control of the ports.
Many people in Tripoli and western Libya criticize Haftar as a new dictator in the making, but he has become a political figurehead for many in the east who feel abandoned by the capital.
In seizing the ports, the LNA displaced units of Libya's Petrol Facilities Guard (PFG) led by Ibrahim Jathran, which struck a deal with the GNA in July to end its three-year blockade of the Ras Lanuf, Es Sider and Zueitina terminals.
The LNA took Ras Lanuf and Es Sider, Libya's biggest export terminals, in a dawn operation on Sunday it dubbed "Swift Lightning". Clashes broke out in Zueitina, but the LNA said overnight that it had secured that port as well as confirming its control of a fourth port, Brega.
Residents in Zueitina and Brega told Reuters that LNA forces were in control on Monday.
A commander allied to the LNA said an attempted counter-attack at Ras Lanuf by Jathran loyalists had been blocked on Monday.
Jathran had lost much local support after switching allegiances to the GNA. There were few casualties during the port seizures as many of his men appeared to have responded to a call from eastern tribal leaders to hand over control peacefully.
Haftar's forces could face a renewed backlash from Islamist-leaning groups in the east as result of the raids, but they have suffered heavy losses in previous battles with the LNA.
His opponents in the western city of Misrata could prove the bigger threat.
Misratan forces are close to finishing a four-month campaign to oust Islamic State from its former North African stronghold of Sirte.
But the campaign has been costly, and Misrata also has to sustain a military presence in several other parts of the west, including Tripoli, where it has provided support for the GNA.
If the LNA retains military control over the terminals, eastern factions it is allied with could make a fresh attempt to export oil independently from the National Oil Company (NOC) in Tripoli.
But previous efforts to do this through the NOC office in Benghazi and funnel money to an eastern branch of Libya's central bank have been blocked by international opposition.
Claudia Gazzini, a Libya expert at International Crisis Group, said it was in Haftar's interests to have a working relationship with the NOC.
"I think this is what he's aiming for – to be the one who reopens the terminals," Gazzini said.
Still, any deal between the LNA and the state oil body could face stiff political opposition from anti-Haftar elements in the GNA's leadership, or Presidential Council, which late on Sunday called the attacks an "unjustified escalation" that would prolong conflict in Libya.
The GNA's Council consists of nine members who were selected on the basis of Libya's political and geographical divisions and are often divided among themselves.
The return to the Council of Ali Gatrani, a member representing the east who had suspended his membership for months, opens a potential channel to Haftar and his allies in the east as the government seeks to win their backing.
In the past, however, eastern factions have said they will not join the GNA without greater representation, guarantees over the leadership of the military, and the relocation of the NOC to Benghazi - demands they are likely to press with more confidence now.
"The view of the LNA is that, now they are taking control and making advances, they will want to see an improvement in their funding, they will want to see this reflected economically and politically in their benefit," said Mohamed Eljarh, an analyst with the Atlantic Council.
In such a scenario, he said, Misrata leaders could refuse to deal with Haftar, adding: "There we could really see the faultlines for the division of the country."
(Additional reporting by Ahmad Ghaddar in London; Editing by Pravin Char)