By Aidan Lewis
TUNIS (Reuters) - A month after it was agreed in Morocco, a U.N.-backed plan for a united Libyan government is struggling to take off.
Efforts to push the hard-fought compromise through show the enduring regional rivalries and power struggles that have bedevilled Libya since the 2011 overthrow of Muammar Gaddafi.
While foreign pressure builds to tackle a threat from Islamic State militants, Libya's internationally recognised parliament, based in the east, has rejected a main article in the U.N. accord as well as a proposed list of ministers.
A rival parliament in Tripoli has yet to make clear whether it will participate and its chief has touted separate negotiations without U.N. involvement.
A new government would need to move to Tripoli in order to exercise power effectively but armed groups hold sway there and brigades of former anti-Gaddafi fighters still settle feuds in the streets with anti-aircraft cannon.
The conflict between the armed groups who loosely back both political sides has left room for Islamic State to take control over Sirte, Gaddafi's home city, and parts of the coast.
This month they attacked Libya's biggest oil terminals and made the most deadly single raid since Gaddafi's fall.
"This government has to fill the vacuum" U.N. envoy Martin Kobler said. "If the politicians are discussing problems day and night and they do not act on the ground, those like Daesh (Islamic State) will use the political vacuum to expand their power."
Any progress was expected to be bumpy. Hardliners in both camps rejected the agreement at the outset. Divisions emerged last week in the Presidential Council, whose nine members were drawn from different regions to steer through the U.N. plan.
One contention has been the proposed government's bloated size and the question of how Libya's fractured political landscape can be represented in a future cabinet.
Prime Minister-designate Fayez Seraj said the expanded list of 32 ministers was the result of the "sharp political polarisation and armed conflict". Critics said it pandered to the wishes of militias and factions that have sought to consolidate their power over the past five years.
One council member who refused to support the proposed government, Omar al-Aswad, said he had argued for a "crisis government" of just 10 members chosen on ability, but had been overruled in a late-night backroom deal.
"The country is burning and citizens are desperate," he told Reuters. "Some think that we should build a modern civilian state based on justice and equality. In contrast, others think in terms of private interests, based on regionalism."
Under the U.N. plan the eastern parliament, the House of Representatives will be the main legislature. It will work with a second chamber, the State Council, formed from the reinstated General National Congress in Tripoli.
When it convened this week the House demanded a government proposal with fewer ministers, although it backed the U.N. plan in principle.
Its objection to a clause that would transfer power over senior security appointments to the new government would also need to be resolved.
The chances of this happening turn on the future role of General Khalifa Haftar, a former Gaddafi ally who leads the armed forces allied to the eastern government but is deeply unpopular in the west.
If political wrangling drags on, pressure may mount from Western powers anxious about Islamic State to back a unity government regardless.
But that would create a risk that the Presidential Council and its government become "a group of people who've been picked and imposed by the international community," said Wolfram Lacher of the German Institute for International Security Affairs.
One way to form a unity government would be to move to Tripoli from Tunis, where the council is currently based.
But securing the Libyan capital is no small task. In the past, militias have stormed government buildings, attacked parliament and even briefly kidnapped a prime minister.
Though some forces have said they support the U.N.-backed plan, senior political figures in Tripoli oppose it and there are plenty of armed factions that could act as spoilers.
Several recent incidents have highlighted the risks.
When the Presidential Council paid a fleeting visit to the city of Zliten after a car bombing earlier this month, it ran into a group protesters who fired over their convoy.
When it named a committee to take charge of security the prime minister of the Tripoli government said this violated military law and ordered an investigation into its members.
Late on Tuesday one faction, the Tripoli Revolutionary Brigade, paraded round the city in more than 100 police vehicles before announcing that a government "imposed by the international community would be considered an invasion".
"If the government enters Tripoli, it will have only one possibility: throwing itself in the arms of militias or armed groups," said Aswad, the council member. "The same scenario that happened previously with former governments will repeat itself."
(This version of the story corrects day of Tripoli parade in penultimate paragraph)
(Additional reporting by Ahmed Elumami in Tripoli)