Joe Biden and Xi Jinping.
San Francisco, CA CNN  — 

President Joe Biden compared Chinese President Xi Jinping to “dictators” during a political fundraiser in California Tuesday night, delivering the unscripted remarks roughly a day after US Secretary of State Antony Blinken said his recent trip had yielded “progress” in repairing the fractured relationship between Washington and Beijing.

“The reason why Xi Jinping got very upset in terms of when I shot that balloon down with two boxcars full of spy equipment in it is he didn’t know it was there. No, I’m serious. That’s what’s a great embarrassment for dictators, when they didn’t know what happened,” Biden told attendees at the fundraiser in the Bay Area, referring to the Chinese spy balloon that the US shot down earlier this year.

The president’s apparently off-message remarks come amid a particularly tense time in US-China relations. Washington’s top diplomat said Monday that the US and China had made “progress” toward bringing relations back on track with both sides agreeing on the need to “stabilize” their bilateral relationship.

China quickly slammed Biden’s remarks, with Chinese Foreign Ministry spokesperson Mao Ning calling them an “open political provocation” on Wednesday and “extremely absurd and irresponsible.”

“The remarks seriously contradict basic facts, seriously violate diplomatic etiquette, and seriously infringe on China’s political dignity,” Mao said.

CNN has reached out to the White House about the president’s comment.

Biden in his remarks also praised Blinken’s work to repair the relationship by reiterating he “did a good job” and adding that improving the relationship would “take time.” At a second fundraiser Tuesday, Biden told donors that US climate envoy John Kerry would also hopefully be making a trip to China “pretty soon” with a focus on the environment.

Blinken – who is the first US secretary of state to visit Beijing in five years – recently wrapped up two days’ worth of meetings in the Chinese capital with top officials, including Xi, which resulted in no major breakthroughs but agreements from both sides to continue further diplomatic engagements.

“We’re not going to have success on every issue between us on any given day, but in a whole variety of areas, on the terms that we set for this trip, we have made progress and we are moving forward,” Blinken said at news conference in Beijing on Monday.

And Biden for his part told reporters as recently as this weekend that he hopes to meet with Xi over the “next several months.”