TOKYO - US President Barack Obama has started a six-day trip to East and South-east Asia. In Japan, the first stop of his four-nation tour, Mr Obama was forced to adjust to a widening policy conflict over how to cope with a rising China.
The way the two nations deal with their differences on this issue in the coming months could have important implications.
Figuratively speaking, the United States and Japan may be sleeping in the same bed, but they are having different dreams. Mr Obama and Japanese Prime Minister Shinzo Abe cannot let this situation continue.
What exactly is it that divides the two nations? To understand, it is important to be familiar with a commonly accepted view in Tokyo about the current world situation.
With US naval hegemony fading, Japan sees China as moving to fill an emerging power vacuum in East Asia. The business-minded President Obama probably wanted the focus of his visit to be on the ongoing Trans-Pacific Partnership (TPP) deal with Japan in order to score political points ahead of mid-term elections in November. Instead, it was overshadowed by differences about how the two allies should deal with China.
Worried about Chinese claims in the East China Sea, the nationalistic Abe administration has adopted a very confrontational stance. It has also been bolstering the nation's defences in the Nansei island chain that includes Okinawa and the disputed Senkaku/Diaoyu islands. It has even tried to strengthen ties with countries and regions surrounding China, such as India, Mongolia, Russia, South-east Asia and Australia.
For the hawkish Abe government, the current Obama administration is a less reliable ally. This time, Mr Obama merely reiterated at a press conference in Tokyo the US position that the Senkaku Islands are administered by Japan and, therefore, fall within the scope of Article five of the US-Japan security treaty.
Mr Obama said that the US is opposed "to attempts to change the status quo by force". But no high-ranking US official has ever explicitly said "the US will fight with Japan once China occupies the Senkaku islands. We will defend Japan", or any comment to that effect.
The lack of a strong commitment from Washington is deepening Tokyo's suspicions about just how important the security alliance is to the US.
There is a growing scepticism among conservative political circles in Tokyo that the US is gradually bending over backward to appease China. Japanese political leaders are frustrated at the implicit US acceptance of China's intensifying efforts to send patrol ships near the Senkakus on an almost daily basis. US officials have certainly not condemned this latest evidence of China's increased assertiveness.
Some Japanese politicians also believe that Mr Obama's pivot to Asia has more to do with Washington's growing economic interest in China's massive markets, rather than concern about the need for new military deployments.
Earlier this month, US Defence Secretary Chuck Hagel even talked about a "new type of military relations" between China and the US, giving a positive assessment of bilateral military ties when he visited Beijing.
In the eyes of the Japanese, more and more US scholars also appear to have yielded to Chinese power. An article by University of Chicago professor John Mearsheimer entitled "Say Goodbye to Taiwan" in the March-April issue of the National Interest shocked Japanese experts. In it, he wrote that Taiwan will eventually have to give up even its present de facto independent status and seek a Hong Kong-style accommodation with Beijing.