WASHINGTON — In his second stern warning to North Korea in a week, Defense Secretary Jim Mattis said that if the regime shoots a missile targeting any U.S. soil, including Guam, war would follow.

In late July, North Korea launched its second intercontinental ballistic missile, and the Pentagon assessed that the test showed North Korea now has the capability to hit the U.S. mainland.

Last week, further concerns were raised as the intelligence community assessed North Korea now has the capability to miniaturize a nuclear warhead to fire on a ballistic missile. 

In the week that followed, both North Korea and the U.S. traded escalating warnings, with North Korea ultimately threatening to fire four missiles at the U.S. island territory of Guam. 

In an off-camera but on-the-record session with reporters Monday, Mattis said a direct attack on Guam would risk war.

“I think if they fire at the United States it could escalate very quickly — that’s called war,” Mattis said. “If they shoot at the United States, I am assuming they will hit the United States. If they do that, it’s game on.”

Mattis was careful to say, however, that if a missile was headed in Guam’s direction but was not necessarily going to hit the territory, the U.S. would take measures to defend itself but he stopped short of saying that the North Korean launch would elicit a response in kind.

“We know within moments where it’s going,” Mattis said. “We’ll know if it’s going toward Guam within moments.”

If it was tracking to be close to Guam, decisions on how to react would require consultation with U.S. allies and the White House, depending on the specific circumstances.