Last Wednesday, Libya's UN-backed unity government (GNA) arrived in Tripoli by boat in an attempt to establish its authority in the country. Since its formation under the Libyan Political Agreement (LPA) in December last year the GNA had been forced to operate out of a hotel in Tunisia.

Prime Minister of Tripoli government, Khalifa Al Ghawi, attends a graduation ceremony of security forces for the Libyan National Army, 24 December 2015

As the unity government arrived in Tripoli, it became clear that an immediate, orderly, peaceful handover of power to the GNA is unlikely. Its first challenge has been to gain control of Tripoli, in particular key ministries and financial institutions. Over recent days, despite threats by Khalifa Al Ghawi, Prime Minister of the Tripoli-based rival government allied to the General National Congress (GNC), support for the unity government has been growing.

Last weekend, the Petroleum Facilities Guard (PFG), a militia that controls key oil export ports in eastern Libya, the National Oil Company (NOC), and the Central Bank (CBL), all pledged support to the unity government. Last Thursday, the UN Security Council had renewed its measures to prevent illicit oil exports from Libya. Control over the country's oil fields and associated revenues, as well as its foreign currency reserves, are key to Libya's economic recovery as well as its security (nearly all of the country's main militias receive state salaries).

So far, a number of militias from Tripoli and Misrata, and at least ten western coastal municipalities, have allied themselves with the new unity government. But alliances are shifting continuously and the rival GNC government remains opposed to the unity government. Much will depend in the next few weeks on the position of key militias in Misrata which are still allied to the GNC, and the security arrangements the new unity government can put in place to ensure its own safety.

However, the greatest challenge to the authority of the GNA lies in eastern Libya.

Until its deputies have approved the LPA, the Tobruk-based House of Representatives (HoR) refuses to cooperate with the new unity government. While 97 deputies unofficially endorsed the GNA on 24 February in a declaration, a lack of quorum has prevented the HoR form holding a formal vote. The position of General Khalifa Haftar, commander of the HoR-allied Libyan National Army (LNA), remains a particular bone of contention within the HoR. Under the LPA, Haftar is to relinquish his post, a condition that is unacceptable to a group of deputies loyal to the LNA. So far, Haftar has not responded publicly to the arrival of the GNA and is likely waiting to see whether the GNA can gain a foothold in Tripoli.

The EU has imposed sanctions against three senior leaders of the two rival governments in order to force both to accept the unity's government authority. These sanctions, and the UN Security Council's endorsement of the GNA, carry considerable risk. They will likely intensify political rivalries within the HoR and heighten opposition towards the UN deal in the east. With the majority of Libya's oil fields located in the east of the country, boosting oil sales without the support of the HoR will be challenging. Moreover, Haftar's forces play a key role in confronting Ansar al Sharia and ISIS  militants in and around Benghazi.

Western countries will undoubtedly welcome the growing support within Libya for the unity government. However, its bet to support the GNA may not prove as successful as it may envisage. The GNA is unlikely to sanction the kind of intervention to target ISIS now being discussed in Western capitals. There is little support for such a move within Libya, and it would further jeopardise the GNA's legitimacy while it is negotiating the transfer of power with its two rival governments. A limited intervention (air strikes, commando raids, and advice by Special Forces to vetted armed groups) without GNA approval would also reflect poorly on its legitimacy.

Western capitals will be uneasy about taking unilateral action against ISIS and, as I pointed out in a previous post, would face a patchwork of local armed actors on the ground. But whether the international community will have the strategic patience and political luxury to wait for a unity government to succeed remains to be seen.

Photo by Hazem Turkia/Anadolu Agency/Getty Images