Washington-- U.S. and British ships and submarines launched the first phase of a missile assault on Libyan air defenses, firing 112 Tomahawk cruise missiles Saturday at more than 20 coastal targets to clear the way for air patrols to ground Libya's air force. The Skanner News Video: Latest Libya News
UPDATE: March 20 1pm PST  Pentagon: Strikes were 'very effective." Full battle reports still coming in but judged very effective at stopping Gadhafi's ground offensive in Benghazi. UN forces patrolling airspace over Libya. "This is an international effort designed to enforce a UN mandate." 
9 am PST Libyan leader Moammar Gadhafi says he will fight a "long war' against the UN forces. Fighter planes are using Italian airfields as bases. Reuters reports that anti-aircraft defenses at the Al Watya air base, 100 miles south of Tripoli were damaged in air strikes. Col. Franklin Childress, US military spokesperson told the BBC that the aim is to attack military targets not civilians. Amr Moussa, Secretary General of the Arab League has criticized the strikes on Egyptian televison. The Arab League has been calling for a no-fly zone for a week, but is concerned now about the impact of the strikes. "What is happening in Libya differs from the aim of imposing a no-fly zone, and what we want is the protection of civilians and not the bombardment of more civilians," Moussa said.
UPDATE: Fresh from a meeting of the UN, where the decision was made to launch attacks on the Libyan leader Moammar Gadhafi, David Cameron made a strong statement in support of the UN decision to intervene. "We have all seen the incredible brutality Moammar Ghadafi has inflicted on his people, " Cameron said.
The  UN decision to launch Cruise missiles at Gadhafi's strongholds had to be done, because "It necessary it is legal and it is right.". 
UPDATE 6pm: CNN reports that in Tripoli people the sound of loud explosions likely signals anti-aircraft gunfire.
In announcing the mission during a visit to Brazil, President Barack Obama said he was reluctant to resort to force but was convinced it was necessary to save the lives of civilians. He reiterated that he would not send American ground troops to Libya.
"We cannot stand idly by when a tyrant tells his people there will be no mercy," he said in Brasilia.
It was clear the U.S. intended to limit its role in the Libya intervention, focusing first on disabling or otherwise silencing Libyan air defenses, and then leaving it to European and perhaps Arab countries to enforce a no-fly zone over the North African nation.
Navy Vice Adm. William E. Gortney, director of the Pentagon's Joint Staff, told reporters the cruise missile assault was the "leading edge" of a coalition campaign dubbed Operation Odyssey Dawn. Its aim: prevent Moammar Gadhafi's forces from inflicting more violence on civilians -- particularly in and around the rebel stronghold of Benghazi -- and degrading the Libyan military's ability to contest a no-fly zone.
"This is not an outcome the U.S. or any of our partners sought," Obama said from Brazil, where he is starting a five-day visit to Latin America. "Our consensus was strong, and our resolve is clear. The people of Libya must be protected, and in the absence of an immediate end to the violence against civilians our coalition is prepared to act, and to act with urgency."
A chief target of Saturday's cruise missile attack was Libya's SA-5 surface-to-air missiles, which are considered a moderate threat to some allied aircraft. Libya's overall air defenses are based on older Soviet technology but Gortney called them capable and a potential threat to allied aircraft.
Also targeted: early warning radars and unspecified communications facilities, Gortney said. The U.S. military has extensive recent experience in such combat missions; U.S. Air Force and Navy aircraft repeatedly attacked Iraq's air defenses during the 1990s while enforcing a no-fly zone over Iraq's Kurdish north.
Cruise missiles are the weapon of first choice in such campaigns; they do not put pilots at risk, and they use navigational technologies that provide good precision.
The first Tomahawk cruise missiles struck at 3 p.m. EDT, Gortney said, after a one-hour flight from the U.S. and British vessels on station in the Mediterranean.
They were fired from five U.S. ships — the guided-missile destroyers USS Stout and USS Barry, and three submarines, USS Providence, USS Scranton and USS Florida.
The U.S. has at least 11 naval vessels in the Mediterranean, including three submarines, two destroyers, two amphibious warfare ships and the USS Mount Whitney, a command-and-control vessel that is the flagship of the Navy's 6th Fleet. Also in the area are Navy P-3 and EP-3 surveillance aircraft, officials said.
Gortney said it would take as long as 12 hours to assess the effectiveness of Saturday's strikes. Then a high-altitude Global Hawk unmanned surveillance plane would overfly the target areas to get a more precise view, the admiral said. He would not say how long the attacks on Libyan air defenses would last, but he stressed that Saturday's assault with cruise missiles was the first phase of a multi-stage mission.
Defense Secretary Robert Gates, who was scheduled to fly to Russia on Saturday afternoon to begin a week-long overseas trip, postponed his departure for 24 hours. Pentagon press secretary Geoff Morrell said Gates decided he should remain in Washington to monitor developments in Libya at the outset of U.S. strikes.
Gates had been skeptical of getting involved in Libya's civil war, telling Congress earlier this month that taking out Libya's air defenses was tantamount to war. Others have worried that the mission could put the U.S. on a slippery slope to deeper involvement in yet another Muslim country — on top of the wars in Iraq and Afghanistan.
Hours after Secretary of State Hillary Rodham Clinton attended an international conference in Paris that endorsed military action against Gadhafi, the U.S. and Britain kicked off their attacks.
At a news conference in Paris, Clinton said Gadhafi had left the world no choice but to intervene urgently and forcefully to protect further loss of civilian life.
"We have every reason to fear that, left unchecked, Gadhafi would commit unspeakable atrocities," she told reporters.
Clinton said there was no evidence that Gadhafi's forces were respecting an alleged cease-fire they proclaimed and the time for action was now.
"Our assessment is that the aggressive action by Gadhafi's forces continues in many parts of the country," she said. "We have seen no real effort on the part of the Gadhafi forces to abide by a cease-fire."
In addition to the three submarines and two destroyers, the U.S. Navy ships in the Mediterranean include two amphibious warships, the USS Kearsarge and USS Ponce, and a command-and-control ship, the USS Mount Whitney.
Associated Press writer Lolita C. Baldor contributed to this report.

BENGHAZI, Libya — The U.S. fired more than 100 cruise missiles from the sea while French fighter jets targeted Moammar Gadhafi's forces from the air on Saturday, launching the broadest international military effort since the Iraq war in support of an uprising that had seemed on the verge of defeat.
The U.S. military said 20 sites were hit as the missile strikes targeted air defense installations on or near the Mediterranean coastline, many in the western half of the country that is Gadhafi's stronghold. The French said they were focusing on the rebel-held east.
President Barack Obama said military action was not his first choice.
"This is not an outcome the U.S. or any of our partners sought," Obama said from Brazil, where he is starting a five-day visit to Latin America. "We cannot stand idly by when a tyrant tells his people there will be no mercy."
Thousands of regime supporters, meanwhile, packed into the sprawling Bab al-Aziziya military camp in Tripoli where Gadhafi lives to protect against attacks.
Bhengazi, Libya--  The U.S. fired more than 100 cruise missiles from the sea while French fighter jets targeted Moammar Gadhafi's forces from the air on Saturday, launching the broadest international military effort since the Iraq war in support of an uprising that had seemed on the verge of defeat.

The U.S. military said 20 sites were hit as the missile strikes targeted air defense installations on or near the Mediterranean coastline, many in the western half of the country that is Gadhafi's stronghold. The French said they were focusing on the rebel-held east.

President Barack Obama said military action was not his first choice.

"This is not an outcome the U.S. or any of our partners sought," Obama said from Brazil, where he is starting a five-day visit to Latin America. "We cannot stand idly by when a tyrant tells his people there will be no mercy."

Thousands of regime supporters, meanwhile, packed into the sprawling Bab al-Aziziya military camp in Tripoli where Gadhafi lives to protect against attacks.
In Brazil, President Obama told press Moammar Gadhafi's continued assault on his own people left the U.S. and its international partners with no other choice. The Pentagon said 112 cruise missiles were launched from US and UK ships and subs, hitting 20 targets.
Obama said military action was not his first choice.
"This is not an outcome the U.S. or any of our partners sought," Obama said from Brazil, where he is starting a five-day visit to Latin America. "We cannot stand idly by when a tyrant tells his people there will be no mercy."
A senior military official said the U.S. launched air defenses Saturday with strikes along the Libyan coast that were launched by Navy vessels in the Mediterranean. The official said the assault would unfold in stages and target air defense installations around Tripoli, the capital, and a coastal area south of Benghazi, the rebel stronghold.
Obama declared once again that the United States would not send ground forces to Libya, though he said he is "deeply aware" of the risks of taking any military action.