Diplomatic friction festered between the United States and China on Wednesday as Beijing charged that U.S. high altitude balloons flew over its Xinjiang and Tibet regions and said it would take measures against U.S. entities that undermine Chinese sovereignty.

Washington and Beijing are locked in a tussle over flying objects after the U.S. military this month shot down what it called a Chinese spy balloon over the coast of South Carolina. Beijing says its balloon was a civilian research vessel mistakenly blown off course, and that Washington overreacted.

This week, China countered that U.S. balloons had flown over its airspace without permission more than 10 times on round-the-world flights since May 2022.

"Without the approval of relevant Chinese authorities, it has illegally flown at least 10 times over China's territorial airspace, including over Xinjiang, Tibet and other provinces," Chinese Foreign Ministry spokesperson Wang Wenbin told a regular daily briefing on Wednesday.

The White House has disputed China's allegations.

Washington has added six Chinese entities connected to Beijing's suspected surveillance balloon program to an export blacklist.

"The U.S. has abused force, overreacted, escalated the situation, and used this as a pretext to illegally sanction Chinese companies and institutions," Wang said.

"China is firmly opposed to this and will take countermeasures against relevant U.S. entities that undermine China's sovereignty and security in accordance with the law," Wang said, without specifying the measures.

The balloon dispute has delayed efforts by both sides to try to patch up frayed relations, although U.S. President Joe Biden has also said that he does not believe ties between the two countries were weakened by the incident.

U.S. Secretary of State Antony Blinken, who postponed a planned trip to Beijing over the balloon, is considering meeting China's top diplomat, Wang Yi, in Munich this week, sources have said.

U.S. Deputy Secretary of State Wendy Sherman said later on Wednesday that communication with China had not stopped, but gave no details about any future high-level meetings.

"We hope when conditions make sense that we will be seeing each other face-to-face again. No announcements today," she said

Sherman reiterated that China's claims about U.S. balloons were false.

"They have now said that there have been a gazillion balloons by the U.S. over China. That is absolutely not true. There are no U.S. government balloons over China," she told an event at the Brookings Institution in Washington.