US Defence Secretary James Mattis is in South Korea on the first foreign trip by a senior official in the Trump administration. Mr Mattis is expected to use the visit to reassure Seoul of continuing US commitment to security deals in the face of threats from North Korea. <br/><br/>While campaigning, Donald Trump accused South Korea and Japan of not paying enough for US military support. He also suggested they could be allowed to arm themselves with nuclear weapons. Both Japan and South Korea rejected this idea. <br/><br/> On the campaign trail, Mr Trump also said he was willing to talk to North Korean leader Kim Jong-un, contradicting long-standing US, South Korean and Japanese policy.<br/><br/>Mr Mattis will be in South Korea until tomorrow, and will hold talks with his Korean counterpart, Han Min-koo, among other officials.