The United States does not accept China's declaration of an air defense zone over disputed islands in the East China Sea, the White House said on Monday.

“We don't accept the legitimacy of what China just announced,” press secretary Jay Carney told reporters, calling the move a “provocative” act.

Carney also defended instructions to U.S. air carriers to follow China’s new rules on the air zone, saying the focus was on protecting travelers and in no way signalled the administration’s acceptance of Beijing’s decision.

China last week declared an air defense zone over a number of islands that are also claimed by Japan and warned that they would intercept any unauthorized aircraft in the region.

The move quickly angered the administration, and the Pentagon responded by sending two B-52 bombers through the disputed airspace. China said it tracked the progress of the bombers but made no effort to block their passage.

The air zone threatens to inflame tensions between China and Japan and comes amid Vice President Joe Biden’s weeklong trip to Asia.

A senior administration official said last week that Biden would “discuss directly” the issue with China and note U.S. disapproval.