U.S. President Barack Obama has left for 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 late Wednesday 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.