The Libyan army will withdraw from Misrata and leave local tribes to resolve the conflict in the country's third largest city either by talks or through force, the deputy foreign minister said.
"The situation in Misrata will be dealt with by the tribes around Misrata and Misrata's residents and not by the Libyan army," Khaled Kaim told journalists.
"We will leave the tribes around Misrata and Misrata's people to deal with the situation, either using force or negotiation."
Kaim said the Libyan army had been given an "ultimatum" to stop the rebellion in the western city, 200 kilometres (120 miles) east of the capital Tripoli.
"There was an ultimatum to the Libyan army: if they cannot solve the problem in Misrata, then the people from (the neighbouring towns of) Zliten, Tarhuna, Bani Walid and Tawargha will move in and they will talk to the rebels. If they don't surrender, then they will engage them in a fight."
Misrata has for weeks been the scene of deadly urban guerrilla fighting between rebels and forces loyal to longtime Libyan leader Colonel Muammar Gaddafi.
"Hundreds of thousands of civilians in Misrata have been caught up in ongoing fighting for seven weeks now," the International Committee of the Red Cross (ICRC) said in a statement.
Kaim said US President Barack Obama's administration had decided to send drones to Libya "to assassinate the people," accusing Washington of "new crimes against humanity" after those he said had been committed in Iraq and Afghanistan.
Obama authorised deployment of missile-carrying drone warplanes over Libya "because of the humanitarian situation," US Defence Secretary Robert Gates said on Thursday, calling the move a "modest contribution" to international coalition efforts there.
The Libyan deputy foreign minister hit out at a senior US senator's visit to Benghazi, the opposition bastion 1,000 kilometres (650 miles) east of Tripoli, saying the Transitional National Council (TNC) did not represent the Libyan people and had "no authority on the ground."
John McCain, a Republican senator who lost the presidential race to Obama in 2008, earlier held talks with TNC leaders, urging the international community to arm and recognise the rebel body as the "legitimate voice" of the Libyan people.