Libya's internationally recognised Prime Minister Fayez Al Sarraj said on Sunday he was not prepared to sit down with eastern commander Field Marshal Khalifa Haftar to negotiate an end to the two-month offensive against Tripoli.
His comments to Reuters suggest low prospects for a ceasefire soon in the battle for Libya's coastal capital, where Mr Al Sarraj and his administration are based.
In the latest turmoil since the toppling of Muammar Qaddafi in 2011, Field Marshal Haftar's Libyan National Army (LNA) force has been trying to capture Tripoli. Fighting has caused havoc in southern suburbs and displaced tens of thousands of people, with the eastern commander saying he is trying to dislodge "terrorists" from the capital.
"I will not sit down again with this person because what he has done in past years shows he won't be a partner in the political process," Mr Al Sarraj , 59, said in an interview with Reuters.
The longest-serving in a succession of Tripoli-based prime ministers since 2011, Mr Al Sarraj has met Field Marshal Haftar, 75, a former general in Qaddafi's army, six times in the past few years.
The last meeting was in February in Abu Dhabi as foreign powers sought to broker a power-sharing deal between the rival eastern and western administrations.
"He was only trying to gain time," Mr Al Sarraj said, pointing out that his rival had sent planes to bomb Tripoli.
Mr Al Sarraj struck a defiant tone, saying his troops, from armed groups in western cities, would continue to fend off Field Marshal Haftar.
"Our primary military goal is to defend Tripoli," he said. "In the coming days there will be positive news ... progress," he added, without giving further details.
Calls from abroad for a ceasefire have fallen on deaf ears, particularly given diplomatic divisions over Libya.
Field Marshal Haftar said his LNA began the Tripoli offensive to drive out terrorist groups. Last month he told French President Emmanuel Macron that he always made a political solution his priority and that he took part in the political dialogue, but he had been forced to lead the offensive because discussions with the parties involved made no progress.
Most Western countries work with Mr Al Sarraj and Turkey recently sent him arms. France and other countries have proposed an unconditional ceasefire – without putting real pressure on Field Marshal Haftar – which would allow his troops to stay in western Libya.
But Mr Al Sarraj's camp has rejected that. "You cannot ask the person defending himself to cease fire," he said.
He also earlier on Sunday proposed a national conference to prepare for elections by year-end. "Libyans should meet to overcome this struggle for power," Mr Al Sarraj said.
The United Nations – which had proposed its own such forum just before the war – and the European Union welcomed the idea. But eastern policymakers allied to Field Marshal Haftar rejected it.
The prime minister said he was concerned the Opec member's oil facilities could become embroiled in the conflict.
Libya produces around 1.25 million barrels a day, the Tripoli-based economy minister told Reuters last week.
"For us, it is very important that oil production continues," he said. "But there are dangers coming from the other side which has turned ports into military positions."
State oil company NOC has repeatedly warned its facilities could become dragged into the conflict. Last week, it accused an LNA commander of arriving with 80 soldiers at the eastern oil port of Ras Lanuf.
The LNA controls all major oilfields and most ports.
Mr Al Sarraj said his forces would avoid attacking any oil facilities even if the LNA was stationed there.
The war was hurting Libya's development and basic services as funding had to be diverted to equip troops and treat the wounded, he said. "There could be a [national power] blackout anytime," he said.
As well as threatening to disrupt oil supplies, there are fears the conflict will increase migration across the Mediterranean to Europe and encourage jihadists to exploit the chaos.