A United States government official says military authorities have increased their monitoring of North Korea amid concerns of a possible missile launch by Pyongyang.

The official, who commented on condition of anonymity, said on Wednesday that the U.S. State Department has decided to station naval vessels at positions where they can monitor North Korea.

U.S. Pacific Command spokesman Bradley Gordon also said authorities are keeping a close watch on North Korea.

Defense Secretary Robert Gates told reporters during a Pentagon briefing on Wednesday that the U.S. will make preparations to shoot down the North Korean Daepodong Two ballistic missile, should Pyongyang proceed with its planned test launch.