( CNN ) -- The U.S. military launched its first airstrikes on Libyan leader Moammar Gadhafi 's air defenses Saturday , a Pentagon official said . `` Earlier this afternoon , over 110 Tomahawk cruise missiles fired from both U.S. and British ships and submarines -- struck more than 20 integrated air defense systems and other air defense facilities ashore , '' U.S. Vice Adm. William Gortney told reporters . He said the majority of the targets were on or near the coast , in the western part of the country . A senior military official said earlier that U.S. Tomahawk missiles landed in the area around Tripoli and Misrata , adding that the action was taken after Gadhafi failed to comply with a cease-fire . `` He 's clearly been on the offensive , '' the official , who was not authorized to speak on the record , said of Gadhafi . `` He said that he was going to do a cease-fire and he continued to move his forces into Benghazi . '' U.S. President Barack Obama confirmed that he had authorized `` limited military action in Libya '' and that `` that action has now begun . '' He is planning for the U.S. portion of the military action in Libya to last just a few days , according to a senior administration official . `` In terms of the heavy kinetic portion of this military action , the president envisions it as lasting days , not weeks , '' said the senior official , who was not authorized to speak about sensitive military matters . `` After that we 'll take more of a supporting role . '' Obama noted that military action `` is not an outcome that the U.S. or any of our partners sought , '' pointing out that Gadhafi was offered the opportunity to comply with an immediate cease-fire . `` But despite the hollow words of his government , he has ignored that opportunity , '' Obama said . `` His attacks on his own people have continued , his forces have been on the move , '' and the danger for the Libyan people has grown . The airstrikes on Gadhafi 's air defenses are the first phase in what will likely be a multiphase military operation . `` At this point we are creating the conditions to be able to set up the no-fly zone , '' Gortney said . The senior military official said earlier that phase two of the mission would include planes flying over Libyan airspace near Tripoli , and in the Mediterranean Sea near Benghazi . The coalition says the no-fly zone imposed as part of a U.N. Security Council resolution aims to prevent further attacks by regime forces on Libyan citizens and opposition groups , especially around Benghazi . In addition to the United States , four nations have publicly announced their participation : the United Kingdom , Canada , Italy and France . Other nations are expected to announce their participation soon . The initial mission will be commanded by U.S. Army Gen. Carter Ham and U.S. Africa Command . The Joint Task Force 's `` Odyssey Dawn '' is being commanded by U.S. Navy Adm. Sam Locklear , on board the USS Mount Whitney in the Mediterranean Sea . `` The use of force is not our first choice , and is not a choice that I make lightly , '' Obama said in a statement from Brazil where he is on a tour of Latin America . `` But we can not stand idly by when a tyrant tells his own people that there will be no mercy . '' From CNN 's Chris Lawrence .
NEW : Tomahawk cruise missiles strike more than 20 targets . NEW : They were fired from U.S. and British ships and submarines . NEW : Obama expects the U.S. portion of the military action to last just a few days , an official says .