US Defense Secretary Chuck Hagel has indicated as much, but it is the first official remark by the president of the United States.
So does he wants a nuclear war with China over some rocks in the ocean?
Looking at the way he was extremely willing to go to a "shock and awe" war with Syria (and Russia that supports the Syrian government) on a flimsy so-called piece of evidence (youtube video) of gas attacks (which turned out to be a false flag operation by the Turkish government, according to Seymour Hersh) and looking at the most recent "regime change" in Ukraine and unfolding mess, yes he is quite willing to risk a war with China, even if not necessarily nuclear.
Mr. Obama denies it is yet another infamous "red line"...
From Reuters (4/24/2014; part, emphasis is mine):
U.S. President Barack Obama assured ally Japan on Thursday that Washington was committed to its defendefensece [sic.], including of tiny isles at the heart of a row with China, but denied he had drawn any new "red line" and urged peaceful dialogue over the islands.
...Obama, on the start of a four-nation tour, is being treated to a display of pomp and ceremony meant to show that the U.S.-Japan alliance, the main pillar of America's security strategy in Asia, is solid at a time of rising tensions over growing Chinese assertiveness and North Korean nuclear threats.
"We don't take a position on final sovereignty determinations with respect to Senkaku, but historically they have been administered by Japan and we do not believe that they should be subject to change unilaterally and what is a consistent part of the alliance is that the treaty covers all territories administered by Japan," Obama said.
A bit convoluted way of saying it himself, but the advance statement before he arrived in Japan is much clearer and stronger.
Also from Reuters (4/23/2014; part, emphasis is mine):
U.S. President Barack Obama has assured Japan that tiny islands in the East China Sea at the heart of a territorial row with China are covered by a bilateral security treaty that obligates America to come to Japan's defence.
Obama gave the assurance in remarks published by the Yomiuri newspaper on Wednesday, hours before he was due to arrive in Tokyo for a visit aimed at reaffirming strong U.S.-Japan ties in the face of rising tensions over China and North Korea.
"The policy of the United States is clear - the Senkaku islands are administered by Japan and therefore fall within the scope of ... the U.S.-Japan Treaty of Mutual Cooperation and Security," Obama said, referring to the disputed islands known as the Senkaku in Japan and the Diaoyu in China.
"And we oppose any unilateral attempts to undermine Japan's administration of these islands," he said.
Reuters Japan's article has an additional take on the Senkaku comments by Obama which does not appear in the English article:
Behind [President Obama's remarks] is the situation in Ukraine. China confronting Japan in East China Sea and the Philippines and other nations in South China Sea conjures the image of Russia that has re-incorporated Crimea in southern Ukraine. In the press conference, President Obama and Prime Minister Abe emphasized the importance of observing the international law, and said they oppose the change of status quo with the threat of force.
That's a good one, Mr. President. Your puppet regime in Ukraine was installed thanks to the use of force by neo-Nazi groups supported by your State Department and USAID.
(Oh wait, does that mean Japan is Ukraine? And Senkaku Island Crimea?)
(Photo from Reuters)