The head of the Libyan parliament, Ageilah Saleh, said there could be no peace talks until Tripoli was captured.
Forces led by Khalifa Haftar launched an offensive on Tripoli in April but the assault stalled in the face of resistance from local armed groups aligned with the UN-recognised government in Tripoli.
Haftar and his backers say they are trying to free the capital from the yoke of militias they blame for destabilising Libya since the fall of Muammar Gaddafi in a NATO-backed uprising in 2011.
Haftar’s critics accuse him of trying to seize power through force and deepening a conflict between factions in the east and west of the sprawling North African country.
The campaign on Tripoli left at least 653 dead and displaced more than 93,000, according to the United Nations, as well as causing extensive material damage.
Saleh said “the campaign to liberate Tripoli is not easy”.
“More than two million Libyans are living in the capital and armed groups are using people and buildings as shields,” Saleh told Reuters in an interview during a visit to Cairo.
He said Haftar’s Libyan National Army (LNA) was refraining from using heavy weapons to limit damage to property.
“The army could have carried out a powerful operation and used all kinds of weapons but these are Libyans and we will save any drop of blood, no matter what.”
He rejected any proposals for the LNA to withdraw or agree to a ceasefire. “The military operation must be resolved. The political solution should come after liberation of the Libyan capital,” said Saleh.
“If someone could get these groups out peacefully, the army would return to barracks,” he added, referring to the Tripoli armed groups.
Haftar’s offensive upended United Nations-led plans to stabilise Libya after years of conflict that have left the oil-rich nation divided and caused living standards to plummet.