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President Obama categorically ruled out on Wednesday a land invasion to oust Libyan leader Muammar al-Qaddafi, as a U.S. military commander told Fox News that one of the strongman's compound had been hit again by coalition airstrikes.

The strikes were the second to target a Qaddafi compound, though the specific location wasn't immediately clear. The military source told Fox News that air defense sites were the intended target, and U.S. commanders "don't track where the regime leader is and very specifically do not target him."

Obama said Wednesday that the United States will be pulling back this week from its dominant role in the international campaign aimed at preventing Qaddafi from attacking civilians. Defense Secretary Robert Gates said the U.S. could turn over control of the operation as soon as Saturday.

Obama was asked in an interview with the Spanish-language network Univision if a land invasion would be out of the question in the event air strikes were to fail to dislodge Qaddafi from power. Obama replied that it was "absolutely" out of the question.

Asked what the exit strategy is, he did not 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."

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"We'll still be in a support role; we'll still be providing jamming and intelligence and other assets that are unique to us, but this is an international effort that's designed to accomplish the goals that were set out in the Security Council resolution," Obama said.

House Speaker John Boehner, R-Ohio, expressed concerns over Obama's handling of the crisis in a letter sent to president Wednesday.

"I and many other members of the House of Representatives are troubled that U.S. military resources were committed to war without clearly defining for the American people, the Congress, and our troops what the mission in Libya is and what America's role is in achieving that mission," Boehner wrote.

"A United Nations Security Council resolution does not substitute for a U.S. political and military strategy. You have stated that Libyan leader Muammar Qaddafi must go, consistent with U.S. policy goals. But the U.N. resolution the U.S. helped develop and signed onto makes clear that regime change is not part of this mission," he continued. "In light of this contradiction, is it an acceptable outcome for Qaddafi to remain in power after the military effort concludes in Libya? If not, how will he be removed from power?"

The White House said Obama will continue to update the American people on U.S. military involvement in Libya in the coming days and that an address to the nation hasn't been ruled out.

Secretary of State Hillary Clinton urged Qaddafi to leave Wednesday, saying his inner circle "should make the right decision."

The U.S. has essentially ended its Tomahawk missile missions in Libya as coalition forces launched air strikes over Libya for a fifth day, targeting sites that support or supply Qaddafi's military around the capital and other cities, defense officials said.

A defense official tells Fox News that the U.S. doesn't plan to launch any more Tomahawk cruise missiles unless they are needed.

"We can fly air missions if we need to take out more air defense systems. We have less expensive means of doing that," the U.S. official told Fox News.

The official says the U.S. is still providing nearly all of the refueling tanker capability to the coalition and intelligence and surveillance from the air. The official also says the U.S. still plans to hand over command to the British and French by next Tuesday.

International forces have also launched new airstrikes near the rebel-held city of Misrata, according to BBC News, as dozens have been killed in fighting in the western city.

"This morning, airstrikes twice hit the airbase where Qaddafi's brigades are based," a resident of Misrata told Reuters.

Some attacks by pro-Qaddafi forces continued in Misrata, where the doctor and rebel leaders said pro-Qaddafi 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.

A doctor in Misrata said Qaddafi's tanks fled after the airstrikes, giving a much-needed reprieve to the besieged coastal city, which is inaccessible to human rights monitors or journalists. The airstrikes struck the aviation academy and a vacant lot outside the central hospital, the doctor said.

Rear Adm. Gerard P. Hueber, chief of staff of Joint Task Force Odyssey Dawn, says they have increased combat operations in the rebel stronghold over the past 24 hours.

Hueber said the coalition was targeting Qaddafi's mechanized forces, his artillery and mobile missile sites as well as ammunition and other military supplies. He said coalition forces have moved west to try to protect Ajdabiya and Misrata.

U.S. officials say forces loyal to Qaddafi continue to advance on opposition-held areas.

"Some of these cities still have tanks advancing on them to attack the Libyan people," Rear Adm. Peg Klein, commander of the expeditionary strike group aboard the USS Kearsarge, told Reuters.

The U.S. bombed the wreckage of the F-15 fighter jet that went down Tuesday, a military official told Reuters.

The wreckage was bombed overnight "to prevent materials from getting into the wrong hands," the U.S. official told Reuters.

The Pentagon said Wednesday that there is no evidence that the U.S.-led assault has caused any civilian casualties.

A British military official says Qaddafi's air force "no longer exists as a fighting force," according to BBC News.

"We have Libyan ground forces under constant observation and we attack them whenever they threaten civilians or attack population centers," Britain's Air Vice Marshal Greg Bagwell told the BBC.

Qaddafi's forces intensified the shelling of rebel positions outside a strategic eastern city as they fought to prevent the opposition from taking advantage of the five-day-old international air campaign to regroup in the east.

Western diplomats, meanwhile, said an agreement was emerging about NATO would take responsibility for a no-fly zone over Libya after the United States which has effectively commanded the operation until now -- reiterated that it was committed to the transition.

In what has become a common pattern, pro-Qaddafi troops who have besieged Ajdabiya -- a city of 140,000 that is the gateway to the east -- attacked a few hundred rebels gathered on the outskirts. The rebels fired back with Katyusha rockets but have found themselves outgunned by the Libyan government's force.

Plumes of smoke rose over the city's skyline.

"The weapons they have are heavy weapons and what we have are light weapons," said Fawzi Hamid, a 33-year-old who joined the Libyan military when he was younger but is now on the rebels' side. "The Qaddafi forces are more powerful than us so we are depending on airstrikes."

Most of eastern Libya is in rebel hands but the force -- with more enthusiasm than discipline -- has struggled to take advantage of the gains from the international air campaign, which appears to have hobbled Qaddafi's air defenses and artillery and rescued the rebels from impending defeat.

The coalition includes the U.S., Canada, several European countries and Qatar. Qatar was expected to start flying air patrols over Libya by this weekend, becoming the first member of the Arab League to participate directly in the military mission.

The Obama administration is eager to relinquish leadership of the hurriedly assembled coalition, but divisions have emerged over who would take over.

A compromise proposal would see NATO take a key role in the military operation guided by a political committee of foreign ministers from the West and the Arab world. Officials said the North Atlantic Council -- NATO's top decision-making body which already has approved military plans for enforcing the no-fly zone -- may decide to start them later Wednesday.

Spanish Defense Minister Carme Chacon endorsed the proposal for handing over control of the Libya operation to a political committee. "We are comfortable with that," she said.

Fox News' Jennifer Griffin and the Associated Press contributed to this report.