Despite international condemnation, North Korea appears to be going ahead with plans to launch a rocket to put a satellite into orbit.
In the latest response, a senior U.S. Navy official says the U.S. military is sending its most advanced radar system to the Pacific region ahead of North Korea's expected launch of a long-range missile in mid-April.
The Sea-Based X-Band Radar has the ability to search and track targets, and can send signals to bases in Alaska and California so that they can intercept potential targets.
The U.S. fears North Korea's launch will be inaccurate and unstable, and that debris from the rocket could fall on neighboring Asian countries.
But the deployment of the radar is seen as a precautionary step.
Earlier, Japan announced that the country would intercept the rocket should the Gwangmyungsung-3 show signs of falling on Japanese soil.
Meanwhile, South Korea says it will respond if the North does in fact fire a missile disguised as a satellite.
Korea's Unification Minister Yu Woo-ik told the Japanese daily Asahi Shimbun that the South would act, but he stopped short of specifying how.
He was also non-commital about whether Seoul would take the issue to the UN Security Council.