Defense Secretary Jim Mattis and Secretary of State Rex Tillerson both said Thursday that the U.S. still has the option of using military force against North Korea despite comments by President Trump's chief strategist.

"I can just assure that in close collaboration with our allies there are strong military consequences if [North Korea] initiates hostilities," Mattis said during a joint meeting with Japan's defense and foreign ministers at the State Department.

Trump warned the regime last week it would be met with "fire and fury" for further provocations with its burgeoning nuclear missile program. But chief strategist Steve Bannon gave an interview published Wednesday and said "there's no military solution."

"Until somebody solves the part of the equation that shows me that ten million people in Seoul don't die in the first 30 minutes from conventional weapons, I don't know what you're talking about, there's no military solution here, they got us," Bannon told the American Prospect.

North Korean leader Kim Jong Un has ordered up a plan to launch missiles near the U.S. territory of Guam and said he will watch U.S. actions before deciding whether to execute it.

"Obviously, any diplomatic effort in any situation where you have this level of threat that we're confronted with, a threat of proportions that none of us like to contemplate, has to be backed by a strong military consequence if North Korea chooses wrongly," Tillerson said. "I think that is the message that the president has wanted to send to the leadership of North Korea."

Both Mattis and Tillerson have pushed for a diplomatic solution that includes China and the international community. They met Thursday with Japan Defense Minister Itsunori Onodera and Foreign Minister Taro Kono to discuss cooperation in countering the North.