WASHINGTON (AP) - A barrage of U.S.-led airstrikes opened the door for Libyan rebels to retake the eastern city of Ajdabiya Saturday, handing President Barack Obama a tangible example of progress as he defends the military action to war-weary Americans.
The administration has been under pressure to better explain why the U.S. was embroiling itself in another Muslim conflict and to clarify what America's continuing role will be as it begins to turn control of the week-old operation over to NATO.
Obama cited "significant success" in the war Saturday, and he and others defended the U.S. intervention as lawful and critical to save thousands of lives and stabilize a strategically vital region in the Middle East.
"The United States should not and cannot intervene every time there's a crisis somewhere in the world," Obama said in his weekly radio and Internet address Saturday. But with Libyan leader Moammar Gadhafi threatening "a bloodbath that could destabilize an entire region ... it's in our national interest to act. And it's our responsibility. This is one of those times."
And Massachusetts Democrat Sen. John Kerry, chairman of the Senate Foreign Relations Committee, said the events in the Middle East could be "the most important geostrategic shift since the fall of the Berlin Wall."
Without military intervention by the U.S. and NATO, "the promise that the pro-democracy movement holds for transforming the Arab world could have been crushed," he said in an opinion piece in The Wall Street Journal.
The Pentagon said U.S.-led forces pounded Libyan ground troops and other targets along the Mediterranean coast and in Tripoli, and the contested cities of Misrata and Ajdabiya in strikes overnight, but they provided no details on what was hit. A Pentagon spokesman, Navy Capt. Darryn James, says there were no Tomahawk cruise missile strikes overnight.
All together, the Pentagon said the U.S. military launched nearly 100 strikes overnight, just slightly higher than a day ago.
"Every day, the pressure on Gadhafi and his regime is increasing," Obama said in the Saturday address, which aired just after Libyan rebels retook Ajdabiya, celebrating in the streets.
Meanwhile, Defense Secretary Robert Gates rejected claims by Gadhafi's regime that innocent Libyans were killed in U.S. air strikes, saying "the truth of the matter is we have trouble coming up with proof of any civilian casualties that we have been responsible for."
In an interview pre-taped for CBS News' "Face The Nation," Gates said there were numerous intelligence reports suggesting the regime was taking bodies of people killed by pro-government forces and placing them at sites attacked by U.S. planes.
Even after a week of U.S.-led air strikes, Pentagon officials say that forces loyal to Gadhafi are a potent threat to civilians. And they 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.
Obama, who will speak to the nation Monday evening, has been roundly criticized by lawmakers for not seeking more Congressional input on the war.
Top State Department lawyer Harold Koh said Saturday that U.S. had "ample international legal authority" to intervene in Libya and all Congressional requirements were met.
He said the "nature, duration and scope" of the operation do "not rise to the level" of requiring anything more than has already been done in terms of US law, he said.
"I wish I lived in a world in which intervention was unnecessary, I don't," he said. He added that, "sometimes non-intervention is failure" citing the Bosnian city of Srebrenica and Rwanda.
Former Libyan ambassador to the United States Ali Aujali called Libya a unique situation.
"If no action will be taken, we will have another massacre in Africa that will be remembered like Srebrenica and Rwanda," he said. "It was the right action at the right time."
U.S.-led forces began missile strikes last Saturday to establish a no-fly zone and prevent Gadhafi from attacking his own people.
American officials have said they won't drop bombs in cities to avoid killing or wounding civilians - a central pillar of the operation. Yet they want to hit the enemy in contested urban areas.
Army Gen. Carter Ham, the U.S. officer in charge of the overall international mission, told The Associated Press, the focus is on disrupting the communications and supply lines that allow Gadhafi's forces to keep fighting in the contested cities.
Ham said in a telephone interview from his U.S. Africa Command headquarters in Stuttgart, Germany, that the U.S. expected NATO would take command of the no-fly zone mission on Sunday, with a Canadian three-star general, Charles Bouchard, in charge. Bouchard would report to an American admiral, Samuel Locklear, in Locklear's role as commander of NATO's Allied Joint Force Command Naples, he said.
But as the Obama administration works to step back in the Libya campaign, it was still not clear Saturday when the U.S. military's Africa Command would shift the lead role in attacking Libyan ground targets to NATO. U.S officials say the alliance is finalizing the details of the transfer this weekend.
Associated Press writers Pauline Jelinek, Matthew Lee, Charles Babington, Richard Lardner and Robert Burns contributed to this report.