South Korea's new president, Lee Jae Myung, will face a pivotal moment on Monday when he meets U.S. President Donald Trump in Washington for their first summit, as the countries' decades-old alliance strains to confront rapid geopolitical changes.

South Korean President Lee Jae Myung is in Tokyo to hold his first full summit with Japanese Prime Minister Shigeru Ishiba in a visit largely aimed at showcasing friendly ties between the two Asian neighbors that now face common challenges from

President Lee Jae Myung, left, and first lady Kim Hea Kyung arrive at Joint Base Andrews in Maryland on Aug. 24 from Tokyo to begin a three-day trip to the United States for a bilateral summit with U.