At the same time, National Security Council spokeswoman Caitlin Hayden said, the United States urged North Korea's leaders "to heed President Obama's call to choose the path of peace and come into compliance with its international obligations."
"Threats and provocative actions will not bring North Korea the security, international respect, and economic development it seeks," she said.
North Korea slams U.S.
The latest tough talk from Pyongyang lashed out at the U.S. military presence in the region.
A spokesman for a North Korean group accused the United States of "hurling" its "nuclear war hardware into the region and pushing the situation on the brink of war," Pyongyang's official news agency reported.
"The U.S. imperialists have pursued ceaseless war moves since their occupation of South Korea, creating a touch-and-go situation several times. But never have they worked so desperately to launch a nuclear war against the DPRK with all type latest nuclear hardware involved as now," a spokesman for the National Peace Committee of Korea said in a written statement. The DPRK stands for the Democratic People's Republic of Korea.
The statement said the United States is "seriously mistaken if it thinks it can frighten the DPRK with such latest weapons." It said "the country will no longer remain a passive onlooker to the U.S. imperialists' frantic moves to ignite a nuclear war."
"Cutting-edge weapons are not a monopoly of the U.S. and gone are the days never to return when it could invade other countries with nukes as it pleased," the statement said. "The U.S. and the South Korean warmongers had better stop their rash actions, deeply aware of the gravity of the prevailing situation."
The movement of missiles
The possible movement of the North Korean missile is "of concern, certainly to the U.S. military and to Japan," said Mark Fitzpatrick, director of the Non-Proliferation and Disarmament Programme at the International Institute for Strategic Studies in London.
He said he believes the missile in question is a Musudan, a weapon the North hasn't tested before that is based on a Soviet system.
The North has medium-range ballistic missiles that can carry high explosives for hundreds of miles. U.S. Defense Secretary Chuck Hagel said Wednesday that the recent North Korean threats to Guam, Hawaii and the U.S. mainland have to be taken seriously.
The medium-range missile will probably take about two weeks to prepare, Fitzpatrick said, which means a potential launch could coincide with the April 15 anniversary of the birth of Kim Il Sung, the founder of North Korea and grandfather of its current leader, Kim Jong Un.
"The concern we have is all you need is that one lucky shot, and that one lucky shot from a North Korean missile could do a lot of damage to our island home," Guam Gov. Eddie Calvo told CNN early Friday.
The U.S. playbook
As a result of the war of words, the Obama administration established a "playbook" of pre-scripted actions and responses to the last several weeks of North Korean rhetoric and provocations, an administration official said Thursday.
The actions included an increased show of U.S. military force during the annual U.S.-South Korea military exercise, the Foal Eagle.
Some of the U.S. military's recent moves -- including the deployment of ballistic missile defenses closer to North Korea -- were not part of the planning.
The latest situation on the Korean Peninsula stems from the North's latest long-range rocket launch in December and underground nuclear test in February.
Tougher U.N. sanctions in response to those moves, combined with joint U.S.-South Korean military exercises in the region, are given by Kim Jong Un's government as reasons to ratchet up its threats in recent weeks.