President Barack Obama has reaffirmed the U.S. treaty commitment to defend Japan, including a group of East China Sea islands claimed by both Tokyo and Beijing.
Following a Thursday meeting in Tokyo with Japanese Prime Minister Shinzo Abe, Mr. Obama explicitly stated the Senkaku Islands fall under the treaty obliging the United States to defend Japan if attacked.
"Let me reiterate that our treaty commitment to Japan's security is absolute, and Article 5 covers all territories under Japan's administration, including the Senkaku Islands."
Mr. Obama stressed the U.S. does not take a position on the sovereignty of the islands, known in China as Diaoyu. But he warned against any unilateral move to change their status quo.
It is the strongest recent statement of support for Japan by a U.S. president regarding the island dispute, which has seriously damaged relations between Japan and China.
Responding to the remarks, Chinese foreign ministry spokesman Qin Gang said nothing will change "the basic reality that the Diaoyu Islands are China's inherent territory." He said Beijing remains determined to protect its "sovereignty and maritime rights."
Japan is the first stop on Mr. Obama's eight-day tour of Asia, which also includes visits in South Korea, Malaysia, and the Philippines.
In their joint press conference, Mr. Obama and Mr. Abe reported progress on negotiations on the long-delayed Trans-Pacific Partnership free trade agreement.
As anticipated, no breakthrough in the talks was announced. Mr. Abe, though, attempted to put a positive spin on the tense negotiations.
"TPP will bring great benefits and will be something that will effect a century. Due to Barack's sincere negotiations with Japan, we have managed to move to a new level towards participation in the TPP."
The talks have stalled over Japan's reluctance to drop tariffs on politically sensitive agricultural products.
Earlier Thursday, Mr. Obama held a private meeting with Emperor Akihito at Tokyo's Imperial Palace. A military honor guard, and children holding U.S. and Japanese flags, greeted the president.
He will later attend a state dinner and tour the historic Meiji Shrine before heading to Seoul, where his talks are expected to focus on North Korea's nuclear program.
In Tokyo, Mr. Obama said North Korea represents "the most dangerous, destabilizing situation in all of the Asia-Pacific region." He said Japan, South Korea and the United States should work together to pressure Pyongyang, noting that China's participation is crucial.
South Korea's military has warned that the North could be preparing to conduct its fourth nuclear test during Mr. Obama's visit to Seoul.
From Seoul, Mr. Obama will head to Malaysia, where he 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 taking office in 2009. He has promised to make the Pacific region a greater economic, diplomatic, and military priority for the United States.