The Obama administration calculates that North Korea may test fire mobile ballistic missiles at any time, based on the most recent intelligence showing Pyongyang probably has completed launch preparations, a U.S. official told CNN on Tuesday.
The administration believes a test launch could happen without North Korea issuing a standard notice to commercial aviation and maritime shipping warning them to stay away from the missile's path, according to the official.
He cautioned that most of the information comes from satellite imagery, so it's impossible to reach a definitive conclusion because the United States has no means to gather information on the ground.
"We hope they issue a notification, but at this point we don't expect it. We are working on the assumption they won't," the official told CNN.
He said the launch could be "imminent," but also cautioned that the United States "simply doesn't know."
The official, along with a Pentagon official, told CNN that the United States has been able to keep satellites over the suspected launch area for most of the past week.
The United States thinks the missiles remain at a point about halfway down the eastern coast of North Korea and are about 10 miles inland.
Imagery has been impeded by some bad weather, which means there is less than perfect knowledge about what is happening on the ground. But based on what the United States has seen, the belief is that the missiles have received their liquid fuel and are ready for launch.
After any launch, U.S. satellites and radars in the region would be able to calculate the trajectory of missiles within minutes and quickly conclude whether they are on a test path headed for open ocean or potentially headed for land areas such as Japan.
The United States and Japan would then have to decide whether to try to shoot the missiles down, the officials said.
The report comes as North Korea issued its latest dispatch of ominous rhetoric Tuesday, telling foreigners in South Korea they should take steps to protect themselves in the event of a conflict.
North Korea's unnerving message advising foreigners to secure shelter or evacuate in case of hostilities came as Japan set up missile defenses in Tokyo and North Korean workers failed to turn up for work in the industrial complex jointly operated by North and South Korea.
In the statement published by state-run media and quoted by CNN, the North's Korea Asia-Pacific Peace Committee reiterated accusations that Washington and Seoul are seeking to provoke a war with Pyongyang.
"Once a war is ignited on the peninsula, it will be an all-out war," the committee said, adding that North Korea doesn't want foreigners in South Korea to "fall victim" to a conflict.
The United States dismissed " North Korea's warning as "unhelpful, however. White House spokesman Jay Carney criticized Pyongyang for more "unhelpful rhetoric that serves only to escalate tensions."