U.S. Defense Secretary Leon Panetta says the NATO air campaign over Libya has exposed "gaps" in the alliances' capabilities.
Panetta told NATO defense ministers in Brussels on Wednesday that the gaps include a shortages of drones, refueling tanks and intelligence specialists.
He said the U.S. had to step in to fill some of the gaps. However, he added that the Libya mission shows that European nations can successfully take the lead role in NATO operations.
The NATO ministers are in Belgium to discuss Libya and other operations in the first of a series of meetings before a May summit in the United States.
On Tuesday, Panetta said not knowing the whereabouts of former Libyan leader Moammar Gadhafi makes it difficult for the alliance to decide when to end its air operation in Libya.
On Wednesday, Libya's provisional government fighters continued to push for control of Sirte, Gadhafi's hometown.
Reuters news agency quotes a provisional government commander who said the National Transitional Council (NTC) fighters had gained control of half of the town, which has been a stronghold for Gadhafi's loyalists.
On Tuesday, Libyan civilians poured out of Sirte, where intense fighting has been underway for three weeks.
NTC leaders have vowed to step down after Sirte is secured and the country's liberation declared.
Some information for this report was provided by AP, AFP and Reuters.