In addition to offering reassuring comments, Mattis was also expected to focus his talks on readiness and coordination in dealing with North Korea.
Mattis's emphasis on the dangers emanating from Pyongyang appears to signal a re-examination of the us approach to North Korea, as leader Kim Jong Un continues his program of missile and nuclear tests and threatens to debut an intercontinental ballistic missile capable of delivering a nuclear weapon to the United States.
Trump had said while campaigning that some allies were not giving their fair share to defense and suggested that North Korea and Japan develop their own nuclear weapons, rather than rely on the US nuclear umbrella, if they weren't willing to pay more for USA military support.
In response to the continued missile and nuclear tests from the Kim regime, the US and South Korea have developed the USA missile defense system, Terminal High Altitude Area Defense (THAAD), which is expected to be deployed in South Korea later this year.
Japanese Prime Minister Shinzo Abe - who is scheduled to meet Trump next week in Washington - told lawmakers he intends to press Mattis about "the significance of the Japan-US alliance". Mattis arrived in the country Thursday on his first foreign trip in his new role; he'll also visit Japan. Hyun-bin, strong words from Mattis, but walk us through what was said.
Mattis then met Acting President and Prime Minister Hwang Kyo-ahn and National Security Office chief Kim Kwan-jin and attended a dinner hosted by Defence Minister Han Min-koo.
Both US and South Korea feel threatened with North Korea's nuclear programme. He reaffirmed a commitment to put a missile defense system known as Thaad in South Korea, accusing Kim Jong Un's regime of "threatening rhetoric and destabilizing behavior".
North Korea's actions have prompted the United States and South Korea to respond by bolstering defenses, including the expected deployment of a USA missile defense system, known as Terminal High Altitude Area Defense (THAAD), in South Korea later this year. "I think there is hope in [South] Korea and Japan that Mattis and [Secretary of State Rex] Tillerson will become a center of gravity for US foreign policy decision making in Asia at least", James Schoff, senior fellow in the Carnegie Asia Program, told Foreign Policy. "The secretary responded that the alliance would continue to take defensive measures in response to this threat developments, such as the stationing of THAAD to Korean Peninsula".
Chinese Foreign Ministry spokesman Lu Kang yesterday reiterated China's opposition to Thaad, which he said would never change.