A Honolulu-based Asia expert called China’s establishment of an "air defense identification zone" over a large sea area a foolish, unenforceable and hollow threat.

The U.S. Air Force promptly sent two unarmed B-52 bombers from Guam, unannounced, through that international airspace Monday without incident.

"It’s just a very quick statement from the United States essentially backing up the words we said (Monday) that this Chinese announcement will not have any impact on how we conduct our operations," said Ralph Cossa, president of the Pacific Forum Center for Strategic and International Studies.

Cossa said the U.S. was almost forced to rebuke China’s declaration of an air defense zone over Japanese-controlled islands in the East China Sea.

"It’s like when the Chinese said, ‘The Yellow Sea is our territorial waters (several years ago), and you are not allowed in without our permission,’" Cossa said.

"Then we had to send an aircraft carrier in there just to remind them that that’s a ridiculous statement and it’s international waters," he said.

The Chinese are trying to put increased pressure on Japan to acknowledge the dispute over the islands called the Senkakus by Japan and Diaoyus by China, Cossa said.

"But they (China) have done it in an extremely foolish way because they’ve done it in a way that has compelled us to become more involved," Cossa said. China also has done it in a way "they cannot possibly enforce," he said.

"We just felt compelled to demonstrate the hollowness (of China’s threat), which we did quickly," Cossa said.