U.S. President Barack Obama has arrived in Japan for the start of a four-nation tour of Asia, where he will try to convince allies that Washington is committed to its "rebalancing" in the Pacific.
Security concerns over China's territorial claims and North Korea's nuclear program will be a major focus of Mr. Obama's trip, which include stops in Japan, South Korea, Malaysia, and the Philippines.
The eight-day tour begins in Tokyo with a meeting with Prime Minister Shinzo Abe. Japan is embroiled in a growing dispute with Beijing over a group of uninhabited islands in the East China Sea.
Ahead of his visit, Mr. Obama told Japan's Yomiuri newspaper the United States opposes "any unilateral attempts to undermine Japan's administration of these islands." He also stressed the islands fall under a treaty that requires the U.S. to defend Japan if attacked.
Mr. Obama will also try to make progress with Japan on the long-delayed Trans-Pacific Partnership free trade deal. But many say Japan's reluctance to drop tariffs on agricultural products makes chances of a breakthrough slim.
From Tokyo, President Obama will head to Seoul, where he will talk with South Korean President Park Geun-hye about how to deal with North Korea, which some believe is preparing to conduct another nuclear test.
The South said Tuesday it detected increased activity at North Korea's nuclear test site. Pyongyang warned last month it was preparing for a "new form" of nuclear test.
In Malaysia, Mr. Obama will hold talks and attend a state dinner with Prime Minister Najib Razak. He will be the first sitting U.S. president to visit Malaysia since Lyndon Johnson traveled there in 1966.
Mr. Obama's last stop will be the Philippines, which is also involved in a territorial standoff with China and has deepened its military cooperation with Washington as a result.
This is Mr. Obama's fifth visit to Asia since assuming office in 2009. He has promised to make the Pacific region a greater economic, diplomatic, and military priority for the United States.