North Korea issued a warning over the weekend to mariners of upcoming live-fire missile exercises. The exclusion zone cited in the notice covers a stretch in the Sea of Japan, 450 kilometers by 110 kilometers (279 miles by 68 miles ) off the coast of Wonsan, North Korea. The warning lasts from June 25 to July 10, from approximately 8 a.m. to 8 p.m. local time, a U.S. counterproliferation official said.

U.S. defense and counterproliferation officials say intelligence suggests that North Korea is likely to fire short- and medium-range missiles, based on the splashdown zone referred to in the notice and other activities that are consistent with such launches.

The officials spoke on condition of anonymity to discuss sensitive intelligence.

If the indications are correct, the U.S. state of Hawaii can rest easy. But in the event North Korea launches a long-range missile, Defense Secretary Robert Gates has ordered the deployment of a ground-based mobile missile intercept system and a radar system to Hawaii. Together they could shoot down an incoming missile in midair.

Experts say North Korea has not yet built a ballistic missile that can reach Hawaii, which is about 4,500 miles (7,200 kilometers) from North Korea.

U.S. defense officials told Congress earlier this month they think North Korea is still three to five years away from being able to hit the West coast of the United States with a long-range Taepodong-2 missile.

If the Taeopodong-2 works as designed, it could travel as far as 4,000 miles (6,400 kilometers), placing parts of the West coast of the United States within range, U.S. officials have said. North Korea's last three missile tests have failed to achieve that distance.

U.S. officials said they have not seen preparations for the launch of a Taeopodong-2 missile similar to that launched on April 5.

It took North Korea about 12 days to stack and fuel that missile, which it claimed was a space-launch vehicle intended to put a satellite into orbit. It failed sometime in its second or third stages, splashing down into the ocean after traveling about 2,000 miles (3,200 kilometers).

Pyongyang has also not mastered mounting a nuclear bomb on a long-range missile despite recently conducting its second underground nuclear test. The yield was estimated by U.S. intelligence as a "few" kilotons.

The communist regime has vowed to bolster its nuclear arsenal and threatened war to protest U.N. sanctions in the wake of its second nuclear test. It conducted its first nuclear test in October 2006, and there are suspicions it is preparing for a third.