The U.S. Missile Defense Agency is conducting a test in the Pacific Wednesday, but an official says the event was long-planned and is not related to tension over a possible North Korean missile launch.  Meanwhile, the U.S. ambassador to the United Nations has rejected a North Korean suggestion for direct talks on the issue.  And there is an unconfirmed media report that U.S. navy ships are moving into position to monitor any North Korean missile launch, and possibly direct weapons to shoot it down.

In this photo provided by the Missile Defense Agency, an interceptor missile is lowered into a silo at Fort Greely near Fairbanks, Alaska (file photo)

Officials say the missile defense test off the coast of Hawaii has been scheduled for a long time and is not related to the tension with North Korea.  Missile Defense Agency spokesman Rick Lehner says the exercise will not even test the type of interceptor that would be used if North Korea ever launched a missile at the United States.

"The one to be tested today is a sea-based version that is designed against short to possibly intermediate range ballistic missiles," he said.  "Any type of long-range ballistic missile attack directed at the U.S. in the future would be dealt with by the long-range interceptors based in California and Alaska."

According to a statement by the Missile Defense Agency, this will be the first test of an improved version of its interceptor missile, which it says is scheduled for operational deployment aboard U.S. navy ships later this year. 

The Sea-Based X-band Radar is so powerful it can identify baseball-sized objects from thousands of miles away (file photo)

The Washington Post newspaper reported Wednesday that U.S. navy ships with special radar capability have been moved into position near North Korea to monitor any missile launch, and potentially to direct interceptor missiles to shoot it down.  But officials will not comment on the specific capabilities or alert status of the missile defense system, which is still in its development and testing phase.

Meanwhile, the number two diplomat at North Korea's mission to the United Nations has suggested direct talks to address U.S. concerns about a possible missile launch.  But on Wednesday U.S. ambassador John Bolton rejected that suggestion.

John Bolton (file photo)

"I must say you don't normally engage in conversations by threatening to launch inter-continental ballistic missiles," said Mr. Bolton.  "And it's not a way to produce a conversation, because if you acquiesce in aberrant behavior you simply encourage the repetition of it, which we're obviously not going to do.  So, main point remains that North Korea should not launch."

North Korea has long sought direct talks with the United States, but U.S. officials say any dialogue must be in the context of six-party talks aimed at ending North Korea's nuclear program.

Ambassador Bolton says if North Korea launches a missile there would "absolutely" be a response stronger than a press release, and that there is broad support for such a response.  But he would not say what that might be, saying consultations are continuing and the priority is to prevent the launch.

Reports from satellite imagery in recent days have indicated preparations for a North Korean launch of a long-range ballistic missile that some analysts believe could reach U.S. territory.

The U.S. missile defense system is designed to respond to such a threat, but the system has had many problems and is not yet fully operational.  Officials say it is a difficult technological challenge to detect, track and destroy a small missile traveling through space at a high rate of speed, and to do so within just a few minutes.  But some tests have been successful, and news reports say the system could get a "real world" test if North Korea goes ahead with its launch.