The Speaker of Libya's alternative parliament said on Wednesday that no peace deal could be reached between rival factions because the capital, Tripoli, had been kidnapped by armed groups.
Aguila Saleh, Speaker of the House of Representatives in Tobruk, said that the self-styled Libyan National Army had stepped in to liberate Tripoli.
The LNA led by Field Marshal Khalifa Haftar, are loyal to the rival government in the east.
It launched a major military offensive this month to capture Tripoli, clashing with militias that support the UN-backed Government of National Accord there.
The offensive has threatened to plunge Libya deeper into chaos and ignite civil war on the scale of the 2011 uprising that toppled and killed longtime dictator Muammar Qaddafi.
"The capital has been kidnapped. The military has stepped in with only one goal, which is to root such groups out of the capital," Mr Saleh told AP in the Egyptian city of Alexandria.
He said it would be impossible to hold next week's UN-planned peace conference under the current conditions.
The UN's national conference set for mid-April was to find a political agreement to restore order in Libya, where lawlessness has led to extremist militancy, human trafficking and instability in the wider region.
Moving towards parliamentary and presidential elections was a major goal of the conference.
Elections in Libya were held shortly after Qaddafi's death but failed to bring stability.
In the years since, Libya has been split between the rival governments and has emerged as a major channel for African migrants hoping to reach Europe.
The International Organisation for Migration said the increased violence in and around Tripoli has led more than 5,800 people to flee their homes.
