The move is considered a sign showing the U.S. is confident that the weeklong assault has been successful.
According to three defense officials, at least one of the five Navy ships and submarines that have collectively launched more than 100 Tomahawk cruise missiles at Libyan targets from positions in the Mediterranean Sea has left the area.
International air strikes late Sunday targeted Gadhafi's hometown of Sirte and the capital Tripoli.
If Gadhafi's hometown falls to rebel control, the advance on Tripoli would become exponentially faster.
Earlier, rebels took back control of two key oil ports. They took Ras Lanouf, the home of a big oil refinery. Rebel forces also seized the oil town of Brega. Coalition air strikes paved the way for the takeovers.
Ras Lanouf and Brega are responsible for large chunks of Libya's 1.5 million barrels of daily exports.
Also Sunday, NATO assumed command of all aerial operations in Libya from the U.S.-led force that has been conducting air strikes against Gadhafi's forces.
NATO jets began enforcing the no-fly zone, Secretary-General Anders Fogh Rasmussen announced. Diplomats said the full transfer of authority would take several days.
The goal of the air strikes is to protect civilians from forces loyal to Gadhafi.
Meantime, Britain's Ministry of Defense released new footage of air strikes on pro-Gadhafi forces.
The British Tornado war planes conducted the strikes in the eastern part of the country. Officials say the attacks took out armored vehicles and rocket launchers.
The rebel turnaround is a boost for President Barack Obama, who has faced complaints from lawmakers from both parties that he has not sought their input about the U.S. role in the conflict or explained with enough clarity about the American goals and exit strategy.
Obama was expected to give a speech to the nation Monday, and U.S. Secretary of State Hillary Rodham Clinton on Sunday defended the administration's decision.
Pentagon officials are looking at plans to expand the firepower and airborne surveillance systems in the military campaign, including using the Air Force's AC-130 gunship armed with cannons that shoot from the side doors, as well as helicopters and drones.
The Associated Press contributed to this story.