By David Morgan
WASHINGTON (Reuters) - U.S. and allied forces have effectively established a no-fly zone over Libya and halted an offensive by Muammar Gaddafi against rebels in Benghazi, the top U.S. military officer said Sunday.
But Admiral Mike Mullen, chairman of the U.S. Joint Chiefs of Staff, told the CBS program "Face the Nation" that the end-game of military action in Libya is "very uncertain" and acknowledged it could end in a stalemate with Gaddafi.
Mullen told NBC's "Meet the Press" program that the U.S.-led air strikes that began Saturday "took out" Gaddafi's air defenses, struck air fields and attacked Libyan ground forces near the eastern rebel stronghold of Benghazi.
"He (Gaddafi) hasn't had aircraft or helicopters flying the last couple days. So effectively that no-fly zone has been put in place," Mullen said.
"We have halted him in the vicinity of Benghazi, which is where he was most recently on the march," he said, adding that Western forces had established combat air patrols over the city that would be extended westward toward Tripoli over time.
Mullen emphasized that Western military operations were narrowly focused on protecting civilians and aiding humanitarian efforts under a U.N. Security Council resolution, not on ending Gaddafi's 41-year rule.
U.S. officials are eager to avoid comparisons between the attacks on Gaddafi's forces and the invasion of Iraq in 2003 that ended President Saddam Hussein's long grip on power.
But Senator Joe Lieberman, a leading U.S. proponent of the no-fly zone, called for Gaddafi to be removed from office.
"Once the president of the United States says, as President (Barack) Obama did, that Gaddafi must go, if we don't work with our allies to make sure Gaddafi does go, America's credibility
and prestige suffers all over the world," Lieberman told CNN.
Mullen, asked whether the Libya operation could end with Gaddafi still in power, told CNN's "State of the Union" program: "I wouldn't speculate how this exactly would come out, and who would be where when."
Asked on CBS if the military operation could end in a stalemate with Gaddafi given its narrow focus and his intransigence, Mullen said, "That's a possibility."
In the next few days, Mullen said, the United States expects to relinquish its leadership of the Libyan operation, dubbed "Odyssey Dawn," which also currently includes Britain, France, Canada and Italy.
But he did not say who would assume the lead.
The U.S. role would then shift to support operations including intelligence, signal jamming, aerial refueling and humanitarian efforts.
U.S. Navy Growlers provided electronic support while AV-8B Harriers from the 26th Marine Expeditionary Unit conducted air strikes against Gaddafi's ground forces and air defenses, the Pentagon said in a statement.
The U.S. military also used B-2 stealth bombers, according to U.S. media reports.
Mullen said Gaddafi has sought to protect targets with human shields. But he added that he had seen no reports of civilian casualties from the air strikes, which Mullen said were calculated to minimize "collateral damage."
There has also been no sign that the Libyan leader intends to mobilize chemical weapons in response to the military operation, Mullen said.
(Additional reporting by Alistair Bell, Missy Ryan and Caren Bohan; Editing by Will Dunham)