Mattis to re-assure Japan, South Korea that Trump won't bite
Mattis to re-assure Japan, South Korea that Trump won't bite · CNBC

U.S. Defense Secretary James Mattis will wrap up talks in South Korea before traveling to Japan later on Friday, as he reminds both countries of Washington's support amid uncertainties over President Donald Trump's policies, a belligerent North Korea and China's territorial ambitions.

It is the first international trip among Trump's cabinet secretaries, according to Reuters, underscoring the importance Trump places on Seoul and Tokyo while he threatens a trade war against Beijing , experts said. The visit should also allay broad concerns about American leadership in Asia and fears over the future of South Korea and Japan's bilateral relationships with the U.S.

"The message of this trip is reassurance; reassurance that the Trump administration recognizes the importance of alliances with South Korea and Japan as well as the seriousness of the security situation there," explained Kathleen Stephens, American ambassador to South Korea from 2008-2011.

During his election campaign, Trump pledged to remove existing American troops from Asia if host nations did not pay 100 percent of the costs—a troubling thought for Seoul and Tokyo, given that defense is a key priority in their respective relationships with Washington. Around 28,000 American soldiers are currently stationed in South Korea, while 54,000 U.S. military personnel are based in Japan.

North Korea top priority in Seoul

North Korea, a common thorn in the sides of Washington, Seoul, and Tokyo, featured prominently in Mattis' talks with top South Korean officials on Thursday. The retired Marine Corps general said that his country would stand "shoulder-to-shoulder" with Seoul to face the North Korean nuclear threat, Reuters reported.

Pyongyang has been increasingly hinting that it is ready to test an intercontinental ballistic missile (ICBM), adding to rising fears it will act on threats of targeting enemies with a nuclear weapon. Choe Kang II, deputy director general for North American affairs at North Korea's foreign ministry told NBC News on Jan. 25 that Pyongyang was ready to test an ICBM "at any time, any place," That same day, Mattis' predecessor Ash Carter warned Washington would shoot down any missile aimed at it or an ally.

North Korean leader Kim Jong Un's nuclear program is a matter crucial to Trump's re-election so Mattis will likely look to discuss ways to disarm the rogue nation as well as deploying preventative measures against potential attacks, said Christopher Hill, former U.S. ambassador to South Korea from 2004-2005.

In July, then South Korean President Park Geun-hye agreed to host a American defense technology system called Terminal High Altitude Area Defense (THAAD), which is designed to shoot down ballistic missiles. But the current political turmoil in Seoul could endanger THAAD implementation .