When US B-52s roared above the Senkaku Islands last Tuesday, the Japanese government viewed the move as a loud and clear message to China over its controversial new East China Sea air defence zone.

The right-leaning Yomiuri, Japan’s biggest daily newspaper, went as far as to claim that “China’s diplomatic isolation is becoming complete”. But the mood shifted on Friday when the US urged its commercial airlines to comply with China’s “air defence identification zone” (ADIZ).

“The signal the US is sending to China and the region is confusing, which is not a good thing,” said Chikako Ueki, an Asia security expert at Waseda University. “The message had been that you cannot change the status quo by force?.?.?.?The key question is whether the US is going to be the defender of freedom of the sea and air, the so-called global commons, as it says.”