U.S. Senator Sam Brownback says North Korea’s attack on South Korea’s “Cheonan” naval vessel could be an indicator that the Pyongyang regime is on the verge of collapse.

The senator made the comment after meeting with Obama administration officials. He urged South Korea, China and the U.S. to prepare for more unstable situations taking place in North Korea.

He added that in addition to reinstituting old sanctions, the U.S. must employ as many new tools as possible to isolate the North Korean regime and to support South Korea.

A leading hard-line congressman on North Korea policy, Brownback also wants Pyongyang back on the list of terrorism sponsors.