NEW : The cruise missiles strike more than 20 targets . UK : They were fired from U.S. and British ships and submarines . NATO : ` 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 . NATO expects the U.S. portion of the military operation to last just a few days , an official says .
NEW : The cruise missiles strike more than 20 targets . UK : They were fired from U.S. and British ships and submarines . NATO : NATO expects the U.S. portion of the military operation to last just a few days , an official says .