James Mattis
James Mattis Reuters

U.S. Defense Secretary James Mattis warned on Monday that an attack by North Korea against the United States could quickly escalate into war, AFP reported.

"If they fire at the United States, it could escalate into war very quickly," Mattis was quoted as having told Pentagon reporters.

He added that the Pentagon is able to tell "within moments" where North Korea's missiles are headed, and said the United States would try to shoot down anything that threatened Guam.

"We will defend the country from any attack at any time from any quarter," stressed Mattis.

If North Korea fires a missile at Guam, "then it's game on, and we will try and do our best to make sure it does not hit the United States," he added.

His comments come amid continued tensions with North Korea. Last week, President Donald Trump warned North Korea it faced "fire and fury like the world has never seen" if it continued to threaten the United States with its missile and nuclear programs.

North Korea was unfazed by Trump’s warning, and responded by threatening a missile attack on Guam, a tiny U.S. territory in the Pacific.

On Friday, Trump tweeted that military options for a potential threat from North Korea are "fully in place," and urged the country's leader, Kim Jong Un, to de-escalate the current confrontation with Washington.

Mattis's comments on Monday came after he and Secretary of State Rex Tillerson said America has "no interest" in regime change in Pyongyang or the accelerated reunification of the two Koreas, and stressed the importance of a diplomatic solution to the crisis.