Secretary of Defense James Mattis will travel to South Korea and Japan on February 1-4. His visit, the first of any Trump official overseas, comes at an important time. North Korea recently threatened to launch an intercontinental ballistic missile (ICBM). Meanwhile, the South Korea-Japan relationship has hit a rough patch, with South Korea protesting Japanese sexual slavery of its women during World War II. Mattis’ visit will be an attempt to shore up this shaky alliance and to deter the North Korean threat.

The U.S. military just concluded naval missile defense drills with Japan and South Korea on January 22, which were focused on countering the North Korean missile threat. The drills were timely, given North Korean leader Kim Jong Un’s ICBM test threat made during his New Year’s Day address. The annual U.S.-South Korea joint military exercises will probably begin in February, and Pyongyang is expected to strongly protest them, as it has in the past. If Mattis is successful, the drill will proceed without change. He could also solidify the U.S. position if the three governments could agree to additional ad hoc military drills, adding in exercises on implementing the United Nations Security Council resolutions, especially provisions on inspections of North Korea-related vessels.

The visit also provides an opportunity for Mattis to deliver a strong message to China, which continues to play a troubling role in North Korea’s proliferation and illicit financial networks. Beijing recently sanctioned South Korea over its decision to deploy the Terminal High Altitude Area Defense (THAAD) system to counter North Korea’s missile program (China does not want the U.S. using the radar to provide early warning for Chinese missile strikes). Mattis should note that China is sanctioning the wrong Korea.

Meanwhile, Japan and China have a dispute over islands in the East China Sea, known as the Senkakus in Japan and Diaoyu in China. Beijing set up an air defense identification zone (ADIZ) there in November 2013. In April 2014, Washington responded by saying that Japan administers the Senkaku islands and they are covered in the U.S.-Japan Treaty of Mutual Cooperation and Security. Mattis should restate this policy and note that Washington will oppose any efforts to undermine Japan’s administration of the islands.

Anthony Ruggiero is a senior fellow at the Foundation for Defense of Democracies. He previously served as a foreign policy fellow in the Office of Senator Marco Rubio and an official at the U.S. Departments of the Treasury and State. Follow him on Twitter @_ARuggiero