WASHINGTON (AP) — NATO agreed to take over command of the newly established no-fly zone over Libya, but the alliance's new role doesn't allow the U.S. to make a quick exit from the costly military operation as the Obama administration had wanted.

American sea and airpower remain key parts of the effort to counter forces loyal to Libyan strongman Moammar Gadhafi after allies balked at assuming complete command of the campaign that began six days ago. The U.S., along with France and Great Britain, maintains primary responsibility for attacks on Gadhafi's ground forces and air defense systems, which are the toughest and most controversial parts of the operation.

The U.S. launched 15 more Tomahawk cruise missiles from naval positions in the Mediterranean Sea, a military official said Friday on condition of anonymity because he was not authorized to speak on the record. The targets late Thursday and early Friday were Scud missile garrisons near Tripoli, while U.S. bombers struck Gadhafi artillery, command and control and tank positions elsewhere, the official said. French and British warplanes attacked an artillery battery and other targets near the town of Ajdabiya, which has been under siege by Gadhafi forces for more than a week.

The Obama administration had sought a clear signal from NATO on the handover of command. Instead, it got a mixed message.

NATO Secretary-General Anders Fogh Rasmussen initially announced the agreement in Brussels, saying the alliance could eventually take more responsibility, "but that decision has not been reached yet." Several NATO members — including Turkey, the alliance's only Muslim member — had resisted any involvement in ground attacks.

After Rasmussen's remarks, Secretary of State Hillary Rodham Clinton praised NATO for taking over the no-fly zone, even though the U.S. had hoped the alliance would take full control of the operation authorized by the United Nations, including the protection of Libyan civilians and supporting humanitarian aid efforts on the ground.

"We are taking the next step: We have agreed along with our NATO allies to transition command and control for the no-fly zone over Libya to NATO," Secretary of State Hillary Rodham Clinton said.

"All 28 allies have also now authorized military authorities to develop an operations plan for NATO to take on the broader civilian protection mission," she added.

Lines of authority were unclear Thursday night, but it appeared the NATO decision sets up dual command centers and opens the door to confusion and finger-pointing. U.S. commanders would presumably be chiefly responsible for ensuring that the NATO protective flights do not conflict with planned combat operations under U.S. command.

Senior administration officials said the agreement came in a four-way telephone call with Clinton and the foreign ministers of Britain, France and Turkey. The four worked out the way forward, which included the immediate transfer of command and control of the no-fly zone over Libya, and by early next week of the rest of the U.N.-mandated mission.

The officials, speaking on condition of anonymity to discuss sensitive military planning, said the actual handover of the no-fly zone would occur in one or two days. They said NATO would have a final operational plan by over the weekend for how it would assume control over the rest of the protection mission, and that it would be executable by Tuesday's meeting in London of nations contributing to the military action.

Clinton also praised the United Arab Emirates for becoming the second Arab country after Qatar to send planes to help the mission to protect Libyan civilians, enforce the U.N. arms embargo on the North African country and support humanitarian aid efforts. The U.A.E. will deploy 12 planes.

The Pentagon, meanwhile, indicated U.S. warplanes will keep flying strike missions over Libya. Navy Vice Adm. William Gortney, staff director for the military Joint Chiefs, told reporters that the American role will mainly be in support missions such as refueling allied planes and providing aerial surveillance of Libya. But the U.S. will still fly combat missions as needed, Gortney said.

"And I would anticipate that we would continue to provide some of the interdiction strike packages as well, should that be needed by the coalition," he added, referring to combat missions such as attacks on Libyan mobile air defenses, ammunition depots, air fields and other assets that support Libyan ground forces.

Associated Press writer Pauline Jelinek contributed to this report from Washington.

Sri Lankan Muslims burn an effigy of President Obama during a protest rally against the allied forces' air strike in Libya, in Colombo, Sri Lanka. (AP Photo/Chamila Karunarathne)