Reported comments by US President Joe Biden describing Chinese leader Xi Jinping as a dictator have been branded "extremely absurd and irresponsible" by an official in Beijing.
The new clash of words comes just over a day since US secretary of state Antony Blinken concluded a visit to Beijing that sought to break the ice in a relationship that has hit a historical low.
Chinese foreign ministry spokesperson Mao Ning said Mr Biden's comments at a fundraiser in California "go totally against facts and seriously violate diplomatic protocol, and severely infringe on China's political dignity".
"It is a blatant political provocation. China expresses strong dissatisfaction and opposition," Ms Mao said at a daily briefing.
"The US remarks are extremely absurd and irresponsible," she added.
Mr Blinken's visit, during which he met with Mr Xi, was aimed at easing tensions between the two superpowers but appeared not to have achieved any solid results.
At the fundraiser on Tuesday night, Mr Biden said that Mr Xi was embarrassed over the recent tensions surrounding a suspected Chinese spy balloon that had been shot down by the Air Force.
"That's a great embarrassment for dictators. When they didn't know what happened," Mr Biden said.
Ms Mao reiterated China's contention that the balloon was intended for meteorological research and had been blown off-course accidentally.
"The US should have handled it in a calm and professional manner," she said.
"However, the US distorted facts and used forces to hype up the incident, fully revealing its nature of bullying and hegemony."