Sen. John McCain said Thursday that the U.S. must be prepared to strike North Korea once it is sure that country can threaten the U.S. with a nuclear weapon.

McCain was briefed on North Korea by the White House Wednesday evening, and when asked on CBS whether he thinks a U.S. military strike against North Korea is imminent, after being briefed on the situation at the White he said, "No."

"But it is clear, and I totally agree, that that option can't be taken off the table," he said. "But it has to be the absolute last option."

"When I say 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," he added.

When pressed, McCain said he would recommend that the U.S. attack North Korea once it is sure that country had a nuclear-armed missile pointed at the U.S.

"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," he said.

"I don't think we could wait til launch," he added. "We do have defensive capabilities that can intercept missiles, but to count on that alone I think would be very risky business."