North Korea's notice to mariners outlines an "exclusion zone" off its coast that's nearly identical to one announced before it tested an anti-ship missile Feb. 25, said Lt. Cmdr. Jeff Davis, a Defense Department spokesman.
"This can be a precursor to some sort of a missile test," Davis said. "We're not overly concerned."
The North Korean missile test last month came on the eve of the inauguration of South Korean President Roh Moo-huyn and amid escalating tensions over Pyongyang's refusal to abandon its nuclear weapons programs.
U.S. officials sought to minimize the significance of that missile test, saying it involved a small weapon and not one of North Korea's stock of long-range ballistic missiles.
Tensions escalated last weekend when North Korean fighters intercepted a U.S. surveillance plane over the Sea of Japan. Last week, Defense Secretary Donald H. Rumsfeld ordered a dozen B-52 bombers and a dozen B-1B bombers transferred to a U.S. base on Guam.
The nuclear dispute intensified in October, when U.S. officials said Pyongyang admitted having a covert nuclear program in violation of a 1994 deal. Washington and its allies suspended fuel shipments; North Korea retaliated by expelling U.N. monitors, withdrawing from the Nuclear Non-Proliferation Treaty and restarting a nuclear reactor.
During a news conference Thursday, President Bush repeated his refusal of direct talks with North Korea, calling the nuclear standoff "a regional issue." The United States believes North Korea already has one or two nuclear bombs.
In an interview earlier this week, Mr. Bush said he wanted to solve the nuclear standoff peacefully but would not rule out a military option.
That statement prompted Pyongyang to claim the U.S. was planning a military strike against its Yongbyon nuclear complex.
North Korea's state-run news agency said Friday that Mr. Bush's remarks were "an undisguised revelation of the U.S. intention to make a pre-emptive strike at the DPRK's nuclear facilities." The initials stand for the North's formal name, the Democratic People's Republic of Korea.
In the interview, Mr. Bush said efforts were underway to persuade China, Russia, South Korea and Japan to work with Washington in seeking a diplomatic solution to the standoff over North Korea's nuclear programs.
If such efforts "don't work diplomatically, they'll have to work militarily," he said. "And military option is our last choice...I believe we can deal with this diplomatically."
The official Central News Agency did not comment specifically on Mr. Bush's call for regional talks, reports CBS Newsman Don Kirk. The commentary, however, repeated North Korea's insistence that the U.S. settle the crisis through dialogue and negotiations directly with Pyongyang.
North Korea also dismissed international concerns over its nuclear facilities, reiterating that they were for the producing electricity.
"As far as the DPRK's operation of its nuclear facilities is concerned, there is nothing to arouse the U.S. concern nor is there anything to cause the international community to worry about it," said Rodong Sinmun, the North's main newspaper.
Meanwhile, South Korea's defense chief said he opposes moving U.S. troops away from the tense border with North Korea before the dispute over the communist state's nuclear program is resolved, while the defense ministry demanded that North Korea stop creating tension through military activity. The defense ministry cited as a prime example the interception of a U.S. spy plane by four North Korean jet fighters last Sunday, 150 miles east of the North Korean coastline.
It was the first official comment by the South Korean government about the episode. South Korea's president has upset U.S. officials by remaining silent on the incident, while suggesting the U.S. not raise tensions by applying too much pressure on the North.
Cho Young-kil said South Korea will consult with Washington to relocate U.S. troops in South Korea "on a long-term basis, considering the security circumstances on the Korean Peninsula."
Defense Secretary Donald H. Rumsfeld indicated Thursday that he wants U.S. troops stationed near the Demilitarized Zone separating North and South Korea to be moved farther from the heavily defended area, shifted to other countries in the region or brought home.
Cho also told a parliament hearing that the rocket North Korea fired off the Korean Peninsula's east coast last week was a new anti-ship cruise missile, but it appeared to have exploded in midair because of defects.
Long-range bombers were deployed this week to Guam as a show of U.S. military might as tensions increased in the standoff over North Korea's nuclear programs.
The Pentagon had ordered the deployment of 12 B-1 and 12 B-52 bombers last Friday to deter conflicts that could arise in the West Pacific, said Lt. David Faggard at the U.S. Pacific Air Force headquarters in Hawaii.