Sen. John McCain, R-Arizona, says that while military action against North Korea doesn't appear to be imminent, it cannot be taken off the table.
Speaking to "CBS This Morning" on Thursday, McCain said a military response to North Korean provocations has to "absolutely be the last option."
"That is when we are convinced that North Korea has that capability to launch a missile that could strike with a nuclear weapon the West Coast of the United States," said McCain.
McCain was one of 100 senators asked to attend a briefing on a the ongoing situation in North Korea at the White House Wednesday afternoon, a meeting he said was an opportunity for the White House and the Senate to understand the options the U.S. currently has in responding to North Korea.
"This is a very serious issue, there's nothing wrong with being called down to the White House to talk about it," said McCain.
"I think they should assume the U.S. will react forcefully but there is a real complication and that is along the DMZ (demilitarized zone) that would range Seoul that complicates things dramatically," McCain added.
The senator noted the role Chinese leadership has in the crisis with North Korea, saying "a lot of the emphasis" has to be on China.
"The Chinese have to really be made aware that this could have a profound effect on our relations with China because if this exchange began the North Koreans very likely could range Seoul with their artillery and that could be catastrophic," said McCain.
When asked when would be the appropriate time for a response to the North Koreans, McCain said, "If it were up to me, I would probably say a missile on the launch pad that we knew for sure had a nuclear weapon on it, I don't know for sure if we could wait to launch, we do have defensive capabilities that can intercept missiles, but to count on that alone, I think would be very risky business."
McCain added that North Korean leader Kim Jong Un is "not a rational person" and that he is "not a person that we can expect to act in a rational fashion."