Washington (CNN) -- A U.S.-led military mission in Libya has effectively imposed a no-fly zone and blasted some of Moammar Gadhafi's ground forces outside the rebel stronghold of Benghazi, Joint Chiefs of Staff Chairman Adm. Mike Mullen said Sunday.
The coalition forces, including U.S., British and French aircraft, have taken out most of Libya's air defense systems and some airfields, Mullen said in interviews on CNN's "State of the Union" program and other networks.
In addition, Libyan ground forces in the vicinity of Benghazi were hit in an effort to prevent attacks on lesser-armed rebel fighters and civilians, said Mullen, who called the start of the mission a success.
"I would say the no-fly zone is effectively in place," Mullen told CNN, adding that the strategy now is to cut off logistical support for Gadhafi's forces that are "pretty spread out" from Tripoli to Benghazi.
Mullen also said Gadhafi's forces had shown little ability to take on the coalition firepower so far, and he made clear that the scope of the mission was limited, involving creation of the no-fly zone, stopping attacks on civilians and allowing humanitarian operations to proceed.
He acknowledged on NBC's "Meet the Press" that the military mission could be completed with Gadhafi still in power.
"He's a thug, he's a cagey guy, he's a survivor. We know that," Mullen said of Gadhafi on the CBS program "Face the Nation," noting that the Libyan leader has access to large quantities of mustard gas that concern the United States.
"It's something he could do a lot of damage with," Mullen said, adding that coalition forces were closely monitoring the situation and, so far, "haven't seen him move in that direction."
U.S. President Barack Obama had been under mounting pressure from Republican critics and some Democrats to take steps against Gadhafi.
On Sunday's talk shows, all U.S. politicians interviewed welcomed the new military mission, but some worried it was too late or too limited to do the necessary job of taking out Gadhafi.
"Isolate, strangle and replace this man -- that should be our goal," Republican Senator Lindsey Graham of South Carolina told "FOX News Sunday."
In particular, Graham took issue with Obama's insistence on getting a U.N. Security Council resolution authorizing the mission as well as Arab League endorsement as a strategy to prevent accusations of a U.S. vendetta against the Islamic world.
"I think the president 'caveated' this way too much, it's almost like it's a nuisance," Graham said. "This is a great opportunity to replace a tyrannical dictator who is not a legitimate leader, who is an international crook. And we should seize the moment and talk about replacing him, not talking about how limited we will be."
However, Mullen and Democrats said gaining international consensus for the mission was crucial, and Mullen made clear that the U.S. role would be limited, telling NBC that "we're not going to put any boots on the ground. This isn't about occupation in any shape or form."
Democratic Senator Jack Reed of Rhode Island told reporters that the best outcome "would be for Gadhafi and his family to recognize that they are illegitimate rulers of the country and to depart the scene, allowing the United Nations, politically, to organize a popular referendum or some democratic means to establish a new government."
"If Gadhafi chooses not to go, then, I think, there will be a longer period of conflict," Reed said. "But I just sense that given this incredible unified opposition to him, particularly the Arab League, that the signal has to be clear that his days are numbered."
For now, Mullen told CNN, "we would like to see him withdraw his forces across the country back into garrison" and stop attacking his people.
When told that Gadhafi was claiming women and children had been killed in the coalition air strikes, Mullen said on CNN that the targets were selected carefully, adding: "I've seen no reports of significant civilian casualties." On other networks, he said he was unaware of any civilian casualties so far.
As part of the no-fly zone, coalition combat aircraft will be patrolling over Benghazi at all times, Mullen told CNN. Coalition forces also are looking to jam communications of Gadhafi's forces in what Mullen called the "first phase of a multifaceted" operation.
"While we're leading it now, we're looking to hand off that leadership in the next few days," Mullen said on NBC. On the same show, Democratic Senator Carl Levin of Michigan, the chairman of the Armed Services Committee, said Britain, France and Arab nations would assume control of the mission.
Mullen said he expected Arab countries that supported the mission to begin contributing military help. On Sunday, the French Defense Ministry announced that Qatar has offered to contribute four fighter planes to the coalition effort.
House Speaker John Boehner, R-Ohio, issued a statement Sunday calling for Obama to provide more explanation on the military mission.
"Before any further military commitments are made, the administration must do a better job of communicating to the American people and to Congress about our mission in Libya and how it will be achieved," Boehner's statement said.
To Republican Senator John McCain of Arizona, Obama waited too long to take action in Libya.
"We need now to support him and the efforts that our military are going to make," McCain told CNN in an interview taped Friday and broadcast Sunday. "And I regret that it didn't -- we didn't act much more quickly, and we could have."
McCain, the ranking GOP member of the Senate Armed Services Committee, said if the United States had acted a few weeks ago, a no-fly zone "would probably have been enough" to prevent the situation in the African country from deteriorating. Even so, he said, time is now against Gadhafi.
"If he (Gadhafi) doesn't succeed in a relatively short period of time, he'll be driven back and, over time, I believe, defeated," McCain said. "I have great confidence in our capabilities that the most mightiest nation in the world is now matched up against a third-rate or fourth-rate power."
Asked if the United States waited too long, Mullen answered that it was impossible to say what might have changed if there had been earlier U.S. action. He emphasized the importance of gaining international consensus and assistance for the military mission launched almost exactly on the eighth anniversary of the U.S.-led invasion of Iraq in 2003, saying: "This wasn't something the United States ginned up."
CNN's Joana Godinho and Gabriella Schwarz contributed to this story