Tokyo:Islands at the centre of a row between Tokyo and Beijing are covered by the US-Japan defence alliance, Barack Obama told a newspaper ahead of his arrival in Tokyo.
Mr Obama, on a tour of Asia that will also take in South Korea, the Philippines and Malaysia, is the first sitting US president to explicitly affirm that hostile action against the island chain would spark an American reaction.
"The policy of the United States is clear - the Senkaku Islands are administered by Japan and therefore fall within the scope of Article 5 of the US-Japan Treaty of Mutual Cooperation and Security," Mr Obama said in a written interview with Japan's
Yomiuri Shimbunnewspaper.
"We oppose any unilateral attempts to undermine Japan's administration of these islands," he said.
Several senior US figures, including former secretary of state Hillary Clinton and Defence Secretary Chuck Hagel, have made similar statements, which Tokyo covets as a way to warn China away from territories it claims as the Diaoyu islands.
Mr Obama's week-long tour of Asia is being dubbed a "rebalancing" eastward of US foreign policy by the White House.
Although China is not on his itinerary, its presence will be felt on every leg at a time of complex regional disputes and questions about US strategy.
On Wednesday, China's state-run Xinhua news agency published a comment piece criticising US policy in the region as "a carefully calculated scheme to cage the rapidly developing Asian giant".
"The United States should reappraise its anachronistic hegemonic alliance system and stop pampering its chums like Japan and the Philippines that have been igniting regional tensions with provocative moves," it said.
The row over ownership of the Senkakus is not new, but has burst to the fore in the past two years, with paramilitary vessels from both sides jostling in nearby waters to assert control.
In November, China declared an air defence identification zone over the East China Sea, including the skies above the islands.
"I've also told (Chinese) President Xi (Jinping) that all our nations have an interest in dealing constructively with maritime issues, including in the East China Sea," Mr Obama told
Yomiuri Shimbun.
"Disputes need to be resolved through dialogue and diplomacy, not intimidation and coercion," he said.
Mr Obama will be striving to show Beijing that the US poses no threat and does not intend to contain it.
"We welcome the continuing rise of a China that is stable, prosperous and peaceful and plays a responsible role in global affairs. And our engagement with China does not and will not come at the expense of Japan or any other ally," Mr Obama said.
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Disputed islands part of US-Japan alliance: Obama
