Fighting in the country erupted two months ago. Rebels control most of the east, while Gadhafi holds the west. However, there are pockets of resistance in western Libya, particularly in the Nafusa mountains.
There were reports that mortar shells from the fighting hit Tunisian territory. New clashes also erupted in the besieged rebel city of Misrata on Wednesday.
France and Italy announced that they would be joining Britain in sending military advisers to help the rebels organize.
France also said it would intensify airstrikes against Libyan military targets after a month of NATO airstrikes has failed to rout Gadhafi's forces.
Libya's foreign minister said that sending military advisers would make the conflict worse. He said that Libya could focus on discussing government changes if the NATO attacks stop.
Meanwhile, the Obama administration has decided to give the opposition $25 million in non-lethal assistance, for vehicles and medical and communications equipment to help protect civilians, according to U.S. officials, who spoke on condition of anonymity because they were not authorized to speak publicly about the aid, which was first reported by The Washington Times.
The Associated Press contributed to this report.