Head of unity government says only united military bringing together all armed factions will be able to defeat ISIS group. TRIPOLI - The head of Libya's unity government said Sunday that only a united military bringing together all the country's armed factions would be able to defeat the Islamic State group. "We are convinced that the only way to end this organisation (ISIS) is through a united military command that brings together all Libyans from every region of the country," Prime minister-designate Fayez al-Sarraj said in a written response to questions. Forces loyal to Sarraj's UN-backed Government of National Accord (GNA) have been fighting since mid-May to oust ISIS from Sirte, 450 kilometres (280 miles) east of the capital Tripoli. Backed by the international community, the GNA set up base in Tripoli at the end of the March but has struggled to assert its control over all of Libya. It has backing from some military units and armed groups mainly from western Libya. But forces based in eastern Libya, including local militias and units of the national army loyal to a controversial general, Khalifa Haftar, have not joined with pro-GNA fighters in the battle against ISIS. Loyalist fighters made significant early advances in the battle to take Sirte, but the offensive has slowed in the face of a fierce ISIS counter-attack. Sarraj said a key reason for the slowdown was care that pro-GNA forces were taking for some 30,000 civilians estimated to still be inside the city. "Victory is only a matter of time. We hope it will come very soon," Sarraj said. Libya descended into chaos after the 2011 uprising that ousted and killed strongman Moamer Gathafi, with the country awash in weapons and rival factions vying for power. ISIS took advantage of the chaos to seize control of Sirte, Gathafi's hometown, in June last year.