News reports suggested Mattis had broken with Trump on North Korea, after Trump tweeted on North Korea, "Talking is not the answer!" and he had later told a reporter: "We're never out of diplomatic solutions".
Seoul says the missile was launched from Sunan, which is where Pyongyang's worldwide airport is, opening the possibility that North Korea launched a road-mobile missile from an airport runway.
"We continue to work together, and the minister and I share a responsibility to provide for the protection of our nations, our populations and our interests, which is what we are here to discuss today", he said during a meeting with South Korean Defense Minister Song Young-moo.
North Korea has made it clear that it sees its weapons program, which demands regular testing to flawless, as the only way to contest decades of USA hostility, by which it means the huge US military presence in South Korea, Japan and the Pacific.
A US ban on travel by Americans to North Korea comes into effect on Friday, a step announced after the death of a USA student shortly after his release from a 15-year prison sentence in the country, where three other Americans are still detained.
Tensions with North Korea have been high all month as the regime has conducted a series of provocative missile tests and Trump threatened to confront North Korean threats.
Bannon, who quickly returned to his role in charge of the right-wing Breitbart News, said there was no realistic way such action could be taken because of the large-scale bloodshed and devastation it would unleash on next-door South Korea, as well as on American military forces stationed in South Korea, Japan and Guam. Three short-range missiles were launched on Saturday.
"We knew within minutes where it was going", he said.
When speaking of the launch, Japan's Prime Minister Shinzo Abo said, "North Korea's reckless action of launching a missile that passed over Japan is an unprecedented, serious and grave threat". North Korea stated the drills were a rehearsal for invasion.
However, China and Russian Federation have both urged calm from all sides and suggested that US military drills in the region may be provoking North Korea.
Constant North Korean provocations do not seriously disturb Seoul-based foreigners like Matthew Crawford either. North Korean leader Kim Jong Un said the launch was a "curtain-raiser of its resolute countermeasures" against the U.S.
Officials say the USS John Paul Jones detected and tracked a medium-range ballistic missile that was launched from the Pacific Missile Range Facility.
This photo, taken on August 2, 2017, shows citizens visiting Imjingak in the South Korean border city of Paju near the Demilitarized Zone separating the two Koreas.