Neither the rebels nor Gadhafi has mustered the force for an outright victory, raising concerns of a prolonged conflict.

Gates said no one was ever under any illusion that the assault would last just two or three weeks. He had no answer when asked about a possible stalemate if Gadhafi hunkers down, and the coalition lacks U.N. authorization to target him.

Obama, when asked about an exit strategy during an interview with the Spanish-language network Univision, didn't lay out a vision for ending the international action, but rather said: "The exit strategy will be executed this week in the sense that we will be pulling back from our much more active efforts to shape the environment."

The administration wants others to lead the way soon: Gates said the U.S. could relinquish control as soon as Saturday. Members of the coalition, however, were still divided over the details.

In a compromise proposal, NATO would be guided by a political committee of foreign ministers from the West and the Arab world. But NATO nations remained deadlocked over the alliance's possible role in enforcing the U.N.-authorized no-fly zone.

NATO warships, meanwhile, started patrolling Wednesday to enforce the U.N. arms embargo against Libya. Alliance spokeswoman Oana Lungescu said the action was to "cut off the flow of arms and mercenaries," activity that intelligence reports say is continuing.

Six vessels were involved the first day, and Canada's Brig. General Pierre St. Amand said 16 ships have been offered by NATO members. Five are from Turkey, the organization's sole Muslim member.

Missiles fired from submarines in the Mediterranean, bombs dropped by B-2 stealth bombers and an array of airstrikes easily totaled hundreds of millions of dollars by the fifth day of the coalition campaign.

Hueber said international forces were attacking government troops that have been storming population centers. On Wednesday evening, Libyan state television reported a "Crusader colonialist bombing targeting certain civil and military locations" in Tripoli's Tajoura district _ scene of some of the heaviest past protests against Gadhafi.

Secretary of State Hillary Rodham Clinton said Gadhafi can end the crisis quickly _ by leaving power. She said the U.S. wants the Libyan government to "make the right decision" by instituting a cease-fire, withdrawing forces from cities and preparing for a transition that doesn't include the longtime dictator.

Some attacks by pro-Gadhafi forces continued in Misrata, where the doctor and rebel leaders said pro-Gadhafi snipers were firing on civilians from rooftops. Abdel-Hafidh Ghoga, a spokesman for the opposition forces, said 16 people were killed today, including five children.

Ghoga said people are being treated "in the hallways of buildings" because they did not dare go outside.

In Zintan, a city of 100,000 about 75 miles (120 kilometers) south of Tripoli, a resident said Gadhafi's forces were shelling from the foot of a nearby mountain, but rebels forced their retreat from all but one side of the city. After five days of fighting, Ali al-Azhari said, rebel fighters captured or destroyed several tanks and seized trucks loaded with 1,200 Grad missiles and fuel tanks. They captured five Gadhafi troops.