North Korea could be preparing for another missile test, Pentagon officials said Friday, citing a warning to ships to stay out of a sector of the Sea of Japan from Saturday to Tuesday.

North Korea's notice to mariners outlines an "exclusion zone" off its coast that is almost identical to one announced before it tested an anti-ship cruise missile Feb. 25, said Lt. Cmdr. Jeff Davis, a Defense Department spokesman.

"Such closures are typically a precursor to a missile launch," Davis said. "While we are not alarmed by this, we don't see how a launch at this time would be particularly helpful, given the increased level of tensions North Korea has already caused."

The test-firing 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 stockpile 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 coalesced 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, 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.

On Friday, Pyongyang claimed the United States was planning a military strike against its Yongbyon nuclear complex. Bush, in an interview earlier this week, had said he wanted to solve the nuclear standoff peacefully but would not rule out a military option.

North Korea's state-run news agency called that statement "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.