The U.N. resolution that authorized international airstrikes against Libya called for Gadhafi and the rebels to end hostilities. Gadhafi announced a cease-fire immediately but has shown no sign of heeding it. His forces continue to attack rebels in the east, where the opposition is strongest.
Meantime, the U.S. is preparing to end its combat missions in Libya on Saturday, allowing other NATO countries to take over airstrikes.
The move comes as Libyan rebels are losing ground against Gadhafi loyalists. Gadhafi forces have once again taken the town of Brega after pushing rebels miles back.
However there are signs the rebels are getting more organized. The rebels had mortars Friday, weapons they previously appeared to have lacked, and on Thursday night they drove in a convoy with at least eight rocket launchers - more artillery than usual.
As the fighting continues in Libya, the U.S. says Britain, France and other NATO countries should be able to handle airstrikes on their own with only U.S. support.
"We have accomplished the military goal and now we need to sustain it in terms of the no-fly zone and in trying to protect the civilian population. You could have a situation in which you achieve the military goal but do not achieve the political goal," said Defense Secretary Robert Gates.
Gadhafi remains defiant, calling on western leaders to step down, saying they are "being affected by power madness."
The Associated Press contributed to this story.