The United States voiced on Sunday its “deep” concern over the fighting near Tripoli as the Libyan National Army (LNA) of commander Khalifa Haftar marched on the capital.
“We have made clear that we oppose the military offensive by LNA forces and urge the immediate halt to these military operations against the Libyan capital,” said Secretary of State Mike Pompeo.
He added that all parties involved have a responsibility to de-escalate the situation as announced by the UN Security Council and G7 group last week.
He urged Libyan factions to return to negotiations, saying that "there is no military solution to the Libya conflict."
The fighting has taken the United Nations by surprise and undermined plans to hold a national conference aimed at reaching agreement on a roadmap for elections to resolve the protracted instability in Libya.
UN envoy for Libya, Ghassan Salame, said the organization is determined to hold the planned conference on April 14-16.
The LNA announced its march west last week to eliminate remaining terrorist and criminal gangs from the region.
The United Nations said Monday 2,800 people had been displaced by clashes and many more could flee, though some were trapped.
LNA forces carried out air strikes on southern Tripoli on Sunday and made progress toward the city center, residents said.
The European Union joined the United Nations, United States and G7 bloc in calling for a ceasefire, a halt to Haftar's advance and return to political negotiations.
France said it had no prior warning of his push for Tripoli and denied it was secretly undermining the peace process, a diplomatic source said, according to Reuters.
A contingent of US forces evacuated at the weekend.
Forces with the Tripoli’s Government of National Accord have announced an operation to defend the capital called "Volcano of Anger".
Allied groups from Misrata along the coast have been moving pickup trucks fitted with machine guns into Tripoli.