12:18
The NATO mission -- called Operation Unified Protector-- includes an arms embargo, a no-fly zone and "actions to protect civilians and civilian centers," the alliance said Thursday.
It follows a U.N. Security Council resolution allowing member states to take all necessary measures -- with the exception of foreign occupation -- to protect civilians under the threat of attack in Libya.
Over the weekend, CNN reported that rebels had taken al-Brega, Ras Lanuf and Bin Jawad and reached a town just east of Sirte. But in the last three days, opposition fighters have been pushed back eastward.
Hoekstra: What may be next in Libya Libyan opposition speaks out on tactics Anderson: Gadhafi opposition badly armed Libyan foreign minister resigns
Rebel forces -- hampered by a lack of organization, training and military know-how when compared to Libyan leader Moammar Gadhafi's troops -- have been demanding an end to Gadhafi's almost 42-year rule in Libya.
But they have been facing sustained attacks and have called for the international community to supply them with better and more powerful equipment.
Saddoun El-Misurati, a spokesman for the Libyan opposition in Misrata, described intense fighting and casualties in the city.
"We managed to get two shipments so far of badly needed medical supplies to the hospitals. But obviously we still need more supplies in dealing with the day-to-day casualties and the situation on the ground," he said.
"Our greatest hope will rely mainly on the support of the international coalition forces in the form of change of tactic from the air to (not only) target tanks and heavy artillery of Gadhafi's forces but also take out groups of snipers positioned on buildings and in the city."
Rebel forces have lost Bin Jawad and the key oil town of Ras Lanuf and are backed up to the al-Brega area, opposition member Col. Ahmed Bani said Wednesday.
Ajdabiya, which is east of al-Brega, will be prepared as a "defense point" if the withdrawal continues farther east, he said.
Weather conditions prevented a NATO-led coalition from launching more airstrikes in an attempt to weaken Gadhafi's ability to attack civilians, a U.S. representative said Wednesday.
While U.S. and British officials say no decision has been made about whether to arm the opposition, a U.S. intelligence source said the CIA is in the country to increase the "military and political understanding" of the situation.
"Yes, we are gathering intel firsthand, and we are in contact with some opposition entities," the source told CNN.
But Robert Baer, a former CIA operative, said on CNN's "AC360" Wednesday night the agency's effectiveness might be limited.
Obama's Libya doctrine Gergen: Libya an improvised intervention Libya state TV slams alleged rape victim
Libya
"I would rather see the Defense Department on the ground, if you have to be there, training," Baer said. "The CIA hates covert action. It rarely works. It worked in Afghanistan, but other times it's almost impossible to do."
Paul Wolfowitz, a former U.S. deputy secretary of defense, said he thinks "we should be doing everything we possibly can to support the opposition," and a prolonged stalemate would be bad for both Libyans who continue to suffer and for the United States.
