The defence secretary also said he believed that the United States had found military options to handle the nuclear crisis on the Korean peninsula that would not put the South Korean capital, Seoul, at grave risk, though he refused to elaborate on what those might be.
At the same time, Mattis appeared unwilling to discuss the matter, saying he "will not go into details" about United States military options and that "I don't want to go into that".
"Yes there are. But I will not go into details", Mattis told reporters at the Pentagon.
But signs that the United States is preparing a military option in North Korea - like a repositioning of military assets or an evacuation of U.S. citizens in the region - have not appeared.
He added, however, that North Korea is deliberately avoiding crossing a line that would "make them vulnerable", and that USA and Japanese missile defenses have been ready to respond.
"If the leadership of a country contemplates the use of force, they must ask themselves: 'Using force against whom, under what conditions, and to achieve what?' " Pinkston said, adding that military options have always been in place to uphold the Korean War armistice and bilateral security alliance commitments with Seoul and Tokyo.
U.S. officials also do not have high confidence that the military could find and destroy North Korea's entire arsenal of long-range missiles and nuclear warheads.
The U.S. and South Korea are technically still at war with North Korea because the 1950-53 Korean conflict ended in an armistice, not a peace treaty. Attacking North Korea could jeopardize our trade connections. "It's a pressurization effort to raise the cost" to Pyongyang of continued testing of missiles and nuclear weapons. Mexico, Peru and Kuwait have either expelled or given notice to ambassadors since the September 3. nuclear test.
His national security adviser, H.R. McMaster, reiterated Sunday on ABC's "This Week", that "all options are on the table" when it comes to addressing the North Korean threat.
The North has also continued to test just how far it can press the USA with its launches and nuclear test, prompting some concerns about American capabilities in the region.
Mattis said the United States and Japan did not shoot it down because it did not pose a direct threat to either nation.
North Korea is "intentionally doing provocations that seem to press against the envelope for just how far can they push without going over some kind of a line in their minds that would make them vulnerable", Mattis said.
It "would elicit a different response from us", if a North Korean missile were to threaten USA or Japanese territory, he said. Other potential options are a naval blockade of North Korea, or a deployment of additional troops to the region.
"We discussed the option, but that's all ..." But he declined to say whether the option is under consideration.
According to U.S. Government teacher, Mr. Kisor, that answer is China.