China's top diplomat on Saturday accused the United States of violating international norms with "hysterical" behaviour, as a running spat over a suspected Chinese spy balloon bubbled to the fore at a global security conference in Munich.

The comments by Wang Yi further clouded the prospects of a meeting between Wang and U.S. Secretary of State Antony Blinken at the sidelines of the gathering. Asked by Reuters later whether he would meet Blinken, Wang smiled and declined comment.

Wang was speaking on the second day of the annual Munich Security Conference, which this year had so far been dominated by the global response to the Russian invasion of Ukraine as the war grinds towards its second year.

U.S. Vice President Kamala Harris later shot back, saying she was troubled that China had deepened its relationship with Russia since the Feb. 24 invasion and that Chinese support to Russia would undermine the rules-based international order.

The spat over the balloon - which flew over the United States and Canada before being shot down on President Joe Biden's orders, hit already strained relations and at a time when the West is closely watching Beijing's response to the Ukraine war.

"To have dispatched an advanced fighter jet to shoot down a balloon with a missile, such behaviour is unbelievable, almost hysterical," said Wang.

"There are so many balloons all over the world, and various countries have them, so is the United States going to shoot all of them down?," he said.

"We ask the U.S. to show its sincerity and correct its mistakes, face up and resolve this incident, which has damaged Sino-U.S. relations."

The balloon spat had prompted Blinken to postpone a planned visit to Beijing. That Feb. 5-6 trip would have been the first by a U.S. secretary of state to China in five years and was seen by both sides as an opportunity to stabilise ties.

On its part, Washington has been hoping to put a "floor" under relations that hit a dangerous low in August with China's reaction to a visit to Taiwan by then-U.S. House Speaker Nancy Pelosi.

Blinken is set to depart Munich on Sunday morning. A failure by the two diplomats to get together in a meeting could be seen as a further blow to the already strained relationship.