Two American B-52 bomber planes flew into an air-defense zone claimed by China without informing Beijing on Monday, U.S. officials said, just days after China demanded that aircraft passing over a disputed island chain in the East China Sea register their flight plans and communication frequencies.

The flights followed Pentagon comments Monday that it wouldn’t adapt its operations to comply with the new Chinese demands. “We will not in any way change how we conduct our operations,” Army Colonel Steve Warren said, as quoted by Bloomberg.

The latest tension in the row, a decades-long conflict over the sovereignty of uninhabited islands near Taiwan that China calls Diaoyu and Japan refers to as Senkaku, has been viewed by Japan and the U.S. — its closest military ally — as an overly aggressive attempt by China to change the regional status quo.

Exactly how China would respond to breaches of the airspace isn’t known, but a boost in military posturing near the islands has heightened fears of an accidental clash.

Fumio Kishida, Japan’s Foreign Minister, said the action could “trigger unpredictable events,” and U.S. Defense Secretary Chuck Hagel added that “the unilateral action increases the risk of misunderstanding and miscalculation.”

[WSJ] [Bloomberg]