Defense Secretary Jim Mattis says the danger posed by a nuclear-armed North Korea is “sobering,” but that a meeting of 20 nations in Vancouver, Canada, this week is focused on finding a diplomatic solution while backing up that effort with a credible threat of military force.

“If the diplomatic option does not work, then obviously the whole point is to reinforce the diplomatic option to show that there are military options should there be a [North Korean] attack,” Mattis told reporters traveling with him Monday to the gathering, jointly hosted by Secretary of State Rex Tillerson and his Canadian counterpart Chrystia Freeland.

“The situation we face I would call it sobering,” Mattis said according to a transcript released by the Pentagon Tuesday. “But this meeting is designed to still make progress diplomatically such as you've seen with three unanimous [U.N.] Security Council resolutions over these last months.”

Mattis, who spoke before arriving in Vancouver Monday, told reporters his role would be to outline the military situation and then depart, leaving the conference in the hands of the diplomats.

“There are military options,” Mattis said, but described the options as designed to strengthen the diplomats' hands.

“That is what we want to have come out of this, let the diplomats know that they are backed up by the force of arms,” Mattis said.

Mattis said the talks between North and South Korea over the North’s participation in next month’s Winter Olympics was a step in the right direction.

“Even if they're starting with the Olympics. They're still some reasons to see the diplomatic initiatives are starting to go in the right direction,” Mattis said.

“I think it is a positive indicator. We just don't know where or how far it goes. Does it have traction? Will it go a long ways or will it go no further than this? I don't know,” he said.

Mattis said the hope is that North Korea will eventually agree to some sort of freeze of both its nuclear and ballistic missile programs, and agree to discussions aimed at a verifiable nuclear-free Korean Peninsula.