U.S. Defense Secretary Jim Mattis says the United States will continue to "hold the line and provide credible military options" to diplomats working to de-escalate tensions on the Korean Peninsula and address Pyongyang's nuclear and missile threat.
Speaking on his flight before landing at Pearl Harbor, Mattis also noted the U.S. was ready to "fight tonight" alongside South Korea, if attacked by the North.
"Those military options have remained since 1953 in place. They remain there today. We could fight tonight, shoulder to shoulder with the South Koreans, if they're attacked," the defense secretary told reporters en route from Vietnam to Hawaii.
Any North Korean attack would be "severely rebuffed," Mattis added.
The Pentagon chief was to meet Friday in Hawaii with South Korean Defense Minister Song Young-moo. Mattis said the meeting would address the policy of a "nuclear-free Korean Peninsula."
The meeting comes as North and South Korea engage in talks about next month's Winter Olympics in South Korea. North Korea has agreed to send a delegation to the games.
Mattis insisted his meeting with Song "was not set up directly because of the Olympics" or the ongoing talks.
Some analysts have said North Korea may be using the talks to attempt to drive a wedge between the U.S. and South Korea.
WATCH: In Hawaii, Mattis Praises Renewed Talks Between South, North Korea
But Mattis pointed out that South Korean officials have promised to limit the talks to Olympics-related topics. He has called the talks a "positive indicator," but questioned how much traction such discussions will have.
The sentiment was echoed by John Merrill, visiting scholar at Johns Hopkins University's School of Advanced International Studies.
"I think it's a huge breakthrough. The problem is how can you maintain this momentum going forward," Merrill said. "The Olympics are going to end in mid-March," and the Paralympic Games follow. "There are actually two sets of games, and the momentum needs to be sustained and increased. So I hope we can do that."
North and South Korea remain in a technical state of war, since their 1950s conflict ended in an armistice, not a peace treaty.
Tensions between North Korea and the U.S. have spiked following Pyongyang's sixth and largest nuclear test in September.
Pyongyang has also continued to advance its ballistic missile program, in hopes of being able to threaten the United States.
In an incident that highlighted public concern about the North Korean threat, Hawaii officials earlier this month inadvertently sent an emergency message warning of an incoming ballistic missile, creating panic among some residents.
U.S. President Donald Trump has threatened to "totally destroy" North Korea, if forced to defend itself or its allies. He has also at various times suggested he is willing to meet with North Korean leader Kim Jong Un.