By defiantly attempting to export their own oil and dispatching troops towards the centre of the country, Libya's eastern factions may be gambling on force as they bid for a larger stake under a UN-backed unity government.

It could be a costly bet, one that ignites renewed conflict between east and west over territory, slashes oil production, and pushes Libya closer to a split that has threatened the country since the uprising that ousted Muammar Gaddafi five years ago.

The unity deal, signed in December despite opposition from hardliners, was meant to end the divide between rival governments in Tripoli and the east who have vied for control over the country and its oil resources since 2014, backed by competing factions of former anti-Gaddafi rebels.

But in an ominous early sign of a possible new showdown, eastern and western factions have sent separate armoured columns towards Gaddafi's home town Sirte, now in the hands of fighters from Islamic State.

Western powers see the unity government as the best hope for ending the chaos.

The Government of National Accord (GNA) has slowly begun to establish itself in the capital since arriving a month ago. But it has done so with the help of armed factions from the western city of Misrata that backed the previous Tripoli government, hardening suspicions among easterners that they will be sidelined.

A claim by the GNA's Presidential Council to leadership over any unified campaign against Sirte drew angry responses from the east, where hardliners already harboured federalist ambitions.

"The nation is facing internal and external conspiracies ... to destroy the army and support the militias in Tripoli," said Ali Al-Qatrani, an ally of the eastern military and one of two Council members who have suspended their membership.

The eastern government's parliament, the House of Representatives, already repeatedly failed to vote to accept the unity government, after rejectionists blocked attempts to even hold a ballot.

Last month, a new oil company set up by the eastern government attempted to ship its first exports of oil without permission from Tripoli. The United Nations responded by blacklisting the tanker carrying 650,000 barrels of crude.

On Tuesday, the east prevented a tanker from loading on behalf of the Tripoli-based National Oil Corporation (NOC), a move that puts production from eastern fields at risk.

Tripoli's NOC has kept the oil industry running since Libya's 2011 uprising, with the income channelled through the Tripoli-based central bank to pay salaries across the country.

"If they can show that the east can sell its own oil and earn its own revenue, that is a hugely damaging step which would lead to reinforcing the view in the east that they can go it alone," said a Western diplomat.

REGIONAL RIVALRIES

After Gaddafi's fall, a gulf between east and west has slowly widened, especially after an alliance of Islamist-leaning Tripoli and Misrata militias took over the capital in 2014 and created their own self-declared government.

The government that had been in place before that revolt decamped to the east, and most of the armed groups that prowl Libya's streets ended up siding with one of the two competing alliances.

As they vied for control of dwindling oil revenues over the past two years, the eastern government tried to set up parallel branches of the National Oil Corporation and the central bank.

It also appointed a former Gaddafi ally, General Khalifa Haftar, as the head of its armed forces, the Libyan National Army (LNA). His role in any national military force as a possible defence minister or army chief has become one of the most divisive problems.

For two years Haftar has been waging a campaign, primarily in Benghazi, the biggest city of the east, against Islamist militants and other former rebels who view him as an Egyptian-backed relic of the old regime with presidential ambitions.

The military leadership has its own divisions, but after a long deadlock the LNA has made significant gains in parts of Benghazi since February, boosting Haftar's popularity and emboldening his political allies.

Residents returning to their homes in areas of Benghazi retaken by the army say they have Haftar and the LNA to thank. Shop assistants offer troops free food and cigarettes, and children pose for photos with soldiers in uniform.

No town, prominent tribe or key politician in the east has "publicly and strongly supported" the unity government or the deal that created it, said Mohamed Eljarh, a non-resident fellow at the Atlantic Council who is based in eastern Libya.

They are holding out for "a different deal, a better deal, that reflects their strength and the advances that they have been making," he said.

After its Benghazi success the LNA says it is getting ready to advance on Sirte from the east, while brigades from Misrata are reportedly preparing to advance from the west.

Eyewitnesses told Reuters that more than 100 LNA vehicles, including ambulances, armoured cars and troop carriers were mobilising, and pictures posted on social media showed dozens of military pick-up trucks on the road south from Misrata.

That prompted the Presidential Council to warn that without coordination, there could be fresh conflict between the two rival forces, to the benefit of Islamic State.

On Tuesday officials said there were skirmishes between the LNA and Misrata-affiliated groups about 300 km (185 miles) south of Sirte.

Political groups were still attempting to salvage a comprehensive deal, but the situation was in "total turmoil", said eastern parliament member Abubakr Buera.

"People in the east are trying to react, they feel like they are being endangered by this political process," he said. "We all agree that Libya needs a single government, but we differ about how to do it."  - Reuters