THE United States and Japan reaffirmed their security alliance yesterday, though visiting President Barack Obama made clear he was not drawing a "red line" when he said Washington would go to Tokyo's defence over islands at the heart of a territorial row with Beijing.
China reacted angrily to the statements, insisting that the islands belong to the mainland, no matter what others say.
Chinese analysts also suggested Mr Obama's comments were aimed at pressuring Prime Minister Shinzo Abe to make concessions on ambitious trade talks that have hit a snag in Tokyo.
There were no signs, however, that the two security allies managed to soothe over their trade disagreements yesterday.
The public rhetoric between the two leaders in fact pointed to palpable frustration on Mr Obama's part with the lack of progress on the Trans-Pacific Partnership (TPP) talks.
"All of us have to move out of our comfort zones and not just expect that we're going to get access to somebody else's market without providing access to our own," he told reporters at a joint press conference with Mr Abe.
"And it means that we have to sometimes push our constituencies beyond their current comfort levels because ultimately it's going to deliver a greater good for all people," he added.
Mr Obama also said the decades-old US-Japan security alliance obliges Washington to defend Tokyo if any territory administered by the Japanese - including the disputed Senkaku/Diaoyu islands in the East China Sea - comes under attack.
However, he hinted at signs of frustration with Japan's handling of the dispute, and reminded Mr Abe of "the importance of resolving this issue peacefully", including not taking "provocative actions".
Mr Abe's visit to the controversial Yasukuni war shrine last December infuriated China and South Korea, both of which see it as a monument to Japan's past militarism. He again irked his neighbours by sending a ritual offering to the shrine early this week, which many also saw as a snub to the US leader ahead of his visit.
So while Mr Abe referred to Mr Obama as "Barack" several times at the press conference to show how they had bonded over Wednesday's sushi dinner, the US leader stuck mostly to "the Prime Minister".
In Beijing, a Foreign Ministry spokesman said the Diaoyu islands are Chinese territory.
"No matter what anyone says or does, nothing changes the fact that Diaoyu islands are Chinese territory and nothing will shake China's or the Chinese people's resolve to defend its sovereignty," said spokesman Qin Gang.
Chinese experts said the US stance was nothing new.
"Everyone knows that this has always been the policy. It's just that the President chose to say it himself," Professor Jin Canrong of Renmin University said, adding he did not expect China to retaliate in a big way.
Professor Shi Yinhong, also from Renmin University, said Mr Obama's explicit mention of "Senkaku" was to try to extract economic concessions from Japan, especially in the TPP talks.
Mr Obama paid a courtesy call on Japan's Emperor and Empress earlier yesterday and later attended a state banquet in his honour.
He leaves today for Seoul, the second leg of his four nation-trip.
Additional reporting by Rachel Chang in Beijing