Here is the latest action the Pentagon has taken in response to any near term launch of a North Korean ICBM:

SBX image via Wikipedia.

The U.S. Pentagon has deployed a giant floating radar in anticipation of an intercontinental missile launch from North Korea, CNN reported Wednesday.

The sea-based X-band radar was deployed in response to North Korean leader Kim Jong-un’s claim in his New Year’s address on Jan. 1 that preparations for an intercontinental ballistic missile have “reached the final stage.”

It has a range of 4,800 km and is capable of monitoring most of China as well as the Korean Peninsula from Okinawa.  [Chosun Ilbo]

You can read more at the link, but the SBX is used to support the US military’s Ground-based Midcourse Defense (GMD) system that has interceptors in Alaska and California that for defense against a limited attack from North Korea.