President Obama hailed the “important progress” of the week-old military intervention in Libya on Saturday, saying that airstrikes by coalition forces had turned back loyalist tanks, saved lives and prevented a humanitarian disaster.

“We’re succeeding in our mission,” Obama said in his weekly radio and Internet address one week after the first foreign bombs and missiles hit the air defenses of Libyan leader Moammar Gaddafi.

With Gaddafi’s troops on the defensive and a no-fly zone firmly in place, the United States is prepared to transfer responsibility for military operations to NATO under the agreement approved by alliance members late Thursday, Obama said.

“This is how the international community should work: more nations, not just the United States, bearing the responsibility and cost of upholding peace and security,” he said.

The president’s remarks came amid reports of new successes by the Libya opposition, as rebel fighters seized the strategic town of Ajdabiya, driving out loyalist forces that had been pounded in recent days by coalition airstrikes. A Libyan government minister confirmed the retreat but also claimed that foreign bombs and missiles had killed civilians.

Obama was expected to deliver a televised speech Monday to defend his administration’s Libya policy, but in his Saturday radio address, he said the military campaign is being waged successfully and in keeping with the core principles of protecting innocent civilians and maintaining strict limits on the United States’ role.

“Today, I can report that, thanks to our brave men and women in uniform, we’ve made important progress,” the president said.

“Because we acted quickly,” he added, “a humanitarian catastrophe has been avoided and the lives of countless civilians — innocent men, women and children — have been saved.”

Obama did not directly call for Gaddafi’s ouster, as the administration has done repeatedly in the past. But he said the Libyan dictator must stop attacks against civilians and pull back his forces. He added that Gaddafi had “lost the confidence of his people and the legitimacy to rule.”

The administration has in recent days been discussing with its allies the possibility of supplying weapons to the Libyan opposition as coalition airstrikes failed to dislodge government forces from around key contested towns, according to U.S. and European officials.

France actively supports training and arming the rebels, and the Obama administration believes the U.N. resolution that authorized international intervention in Libya has the “flexibility” to allow such assistance, “if we thought that were the right way to go,” Obama spokesman Jay Carney said Friday. It is a “possibility,” he said.

Gene Cretz, the recently withdrawn U.S. ambassador to Libya, said that administration officials were having “the full gamut” of discussions on “potential assistance we might offer, both on the non-lethal and the lethal side,” but that no decisions had been made.

The coalition has stepped up its outreach to the opposition, inviting one of its senior leaders to a high-level international conference in London on Tuesday, called to determine future political strategy in Libya.

Increased focus on aiding the rebels came as NATO reached final agreement on taking over command and control of all aspects of the Libya operation, including U.S.-led airstrikes against forces loyal to Libyan leader Moammar Gaddafi. Canadian Lt. Gen. Charles Bouchard, at NATO’s Joint Forces Command headquarters in Naples, Italy, is expected to take command of the operation early next week.

The NATO decision, made late Thursday, followed days of debate over the scope of alliance participation and came in time for President Obama to brief a bipartisan group of nearly two dozen congressional leaders in a call Friday afternoon.

Obama has scheduled a speech at the National Defense University on Monday night “to update the American people” on actions taken “with allies and partners to protect the Libyan people . . . the transition to NATO command and control, and our policy going forward,” the White House announced.

Unlike a week ago, when the White House discouraged questions during a briefing for lawmakers as the Libya mission began, Obama entertained queries from lawmakers during an hour-long call Friday. He was asked repeatedly about the goal of the operation and how long it would take.

His emphasis on the mission’s humanitarian objectives, and plans to decrease U.S. involvement as other nations increase their roles, appeared to satisfy some, but not all.

Sen. Carl Levin (D-Mich.) called Obama’s presentation “very clear, very strong” and said he expected strong bipartisan support. House Speaker John A. Boehner (R-Ohio) said through a spokesman that he appreciated the update but wanted more clarity “on the military objective in Libya, America’s role, and how it is consistent with U.S. policy goals.”

The United States has flown the majority of the combat air sorties over Libya since strikes began last weekend. The administration has been eager to hand off both its lead combat role and overall operational command in keeping with Obama’s portrayal of the operation as an international humanitarian mission.

Arab support for the effort has been a key selling point, and the Pentagon announced that fighter planes from Qatar had participated for the first time Friday in no-fly patrols over Libya. The United Arab Emirates also announced it would send F-16s for the patrols.

The Arabs are not expected to participate in ongoing combat strikes being flown by U.S, French and British forces. In a Pentagon briefing, U.S. Vice Adm. Bill Gortney, director of the Joint Staff, said that allied warplanes had flown 153 missions and launched 16 additional Tomahawk cruise missiles at Libyan forces and installations in the past 24 hours.

But Gortney said that so far the attacks had not had a discernible impact on the ability of Gaddafi’s forces to fight and attack Libya’s cities.

“We have seen a degradation in [Libya’s] ability to command and control their forces as a result of the fires we are putting out there,” Gortney said. “But we haven’t seen it have a large enough effect that is changing the total effect on the battlefield.”

As U.S. and allied forces bring in more surveillance aircraft, he said, they should be able to mount more lethal attacks on Gaddafi’s ground forces.

Officials have said that no consideration is being given to the use of allied ground forces to push out Gaddafi loyalists. But if the current stalemate on the ground continues, the U.S. could bring in slower-moving AC-130 gunships, attack helicopters or armed drones that can mount more discreet strikes and are better suited to battles in urban terrain.

“Those are all weapons in our toolbox that are being considered,” Gortney said.

Rebel officials said that coalition airstrikes against pro-Gaddafi forces partially surrounding the contested eastern Libyan town of Ajdabiya failed to dislodge them, although al-Jazeera reported Friday night that government forces on the eastern side of the town had been overwhelmed and either been taken prisoner or retreated to the west.

The two sides have been shelling each other for a week. Rebel forces have been using the reprieve brought by the airstrikes to regroup and ask for additional weapons from “friendly nations,” said Mustafa Gheriani, spokesman for the Benghazi-based opposition Interim National Council.

A number of officers and soldiers from Gaddafi’s army and air force have defected to the rebels, some taking their weapons with them — including aircraft — and the opposition has seized munitions from captured government bunkers. But the bulk of the rebel force is largely untrained and disorganized, without anti-tank or long-range weapons.

International opponents of arming the rebels have said that both the identity and the aims of the opposition are too uncertain, or that the arms embargo authorized by the United Nations applies to both the Gaddafi government and the rebels.

“I think I am right in saying that the resolution is clear,” British Prime Minister David Cameron told Parliament on Monday. “There is an arms embargo, and that arms embargo has to be enforced across Libya.” Legal advice “suggesting that perhaps this applied only to the regime,” Cameron said, “is not in fact correct.”

A Western diplomat, speaking on the condition of anonymity about disagreements within the coalition, said there is a “legal debate about whether we can or not [arm the rebels]. . . . It would be a big step to go down that route,” the diplomat said.

Both the United States and France, in closed-door discussions, have cited legal “flexibility.” Susan Rice, the U.S. ambassador to the United Nations, told the Security Council that the language in U.N. resolution authorizing international action to protect Libyan civilians “is not specific,” one council diplomat said.

Portuguese U.N. Ambassador Jose Filipe Moraes Cabral, who heads the U.N. Security Council’s Libya sanctions committee, agreed Friday that the applicable wording of the resolution was “open to a lot of interpretation,” Reuters reported. Asked whether it allowed arms shipments to the rebels, Cabral said “I would not interpret it that way.”

Staff writers Tara Bahrampour in Benghazi, Libya, Colum Lynch at the United Nations and Greg Jaffe and Felicia Sonmez in Washington contributed to this report.