The new clash of words comes just over a day after 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.

Foreign Ministry spokesperson Mao Ning said 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,” Mao said at a daily briefing.

“The U.S. remarks are extremely absurd and irresponsible,” Mao said.

Blinken’s visit, during which he met with Xi, was aimed at easing tensions between the two superpowers but appeared not to have achieved any solid results.

Biden, at the fundraiser on Tuesday night local time, said that Xi was embarrassed over the recent tensions surrounding a suspected Chinese spy balloon that had been shot down by the Air Force over the East Coast.

“That’s a great embarrassment for dictators. When they didn’t know what happened,” Biden said.

Mao reiterated China’s contention that the balloon was intended for meteorological research and had been blown off course accidentally.

“The U.S. should have handled it in a calm and professional manner,” she said. “”However, the U.S. distorted facts and used forces to hype up the incident, fully revealing its nature of bullying and hegemony.”

Blinken’s visit had been originally scheduled for February, but was put on hold after the balloon incident. While it marked a return to high-level contacts between the sides, China continues to refuse talks between their militaries.

In recent days, the U.S. says Chinese warplanes and naval ships have maneuvered in threatening ways to their U.S. counterparts in the Taiwan Strait and South China Sea, despite agreements between them on protocols for avoiding such incidents.

During Blinken’s visit, China reiterated its strong objections to U.S. support for the self-governing island democracy of Taiwan, which Beijing claims as its own territory. The U.S. has also sought to block Beijing’s access to cutting-edge computer chip manufacturing technology that could be used for military purposes, and accused China of stealing American intellectual property.

After meeting with Xi on Monday, Blinken acknowledged entrenched differences. “We have no illusions about the challenges of managing this relationship. There are many issues on which we profoundly, even vehemently, disagree,” he said.