China’s foreign ministry said on Friday that the United States had refused to reply to a Chinese request for information on the balloon that it had shot downed off the coast of South Carolina earlier this month.

The Chinese balloon, which Beijing denies was a government spy vessel, spent a week flying over the United States and Canada before President Joe Biden ordered it to be shot down. The episode strained further ties between Washington and Beijing, leading America’s top diplomat to postpone a trip to China.

“The United States, from the recovery of the (balloon) remains to the analysis of the (balloon) debris, has completely acted on its own and in a surreptitious manner,” the foreign ministry’s spokesperson Wang Wenbin told a regular briefing.

“China early on through protected consular channels clearly demanded the United States notify (China) on the progress (of recovery of the balloon), but the United States refused to respond.”

Wang’s comments were made in response to a question about an ongoing US investigation into the balloon.

China said that the alleged spy balloon is a civilian airship used for meteorological purposes, and that it was accidentally blown off course into US airspace.

The United States has said a Federal Bureau of Investigation Laboratory in Virginia is analysing debris from the balloon for “counterintelligence exploitation.”

Both the State Department and the Pentagon have said they had reached out to their Chinese counterparts after the suspected spy balloon was shot down on Feb. 4, in an attempt to keep lines of communication open.

The Chinese defence ministry later said it declined a proposed phone call with the Pentagon because the United States had not created the “appropriate atmosphere”.