A government source says North Korea is believed to be transporting additional equipment necessary to launch its Daepodong Two missile to a launch site in Hwadae County, North Hamgyeong Province.

The source says trucks carrying the equipment have been spotted leaving a munitions plant near Pyongyang headed for the site. It said preparations for a launch are likely under way.

A senior U.S. official also told CNN that a spy satellite image shows North Korea assembling telemetry equipment, essential to test firing missiles, at the site within the last several days.

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 ballistic missile, should Pyongyang proceed with its test launch.

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