Kentfield, California - US President Joe Biden equated his Chinese counterpart Xi Jinping with "dictators" on Tuesday as he addressed a Democratic Party donors reception.

Speaking at a campaign fundraiser in Kentfield, California, Biden said Xi had been angered over an incident in February when an alleged Chinese spy balloon flew over the US before being shot down by American military jets.

"The reason why Xi Jinping got very upset in terms of when I shot that balloon down with two box cars full of spy equipment is he didn't know it was there," Biden said.

"I'm serious. That was the great embarrassment for dictators, when they didn't know what happened."

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"That wasn't supposed to be going where it was... and he didn't know about it," Biden said of Xi. "When it got shot down he was very embarrassed and he denied it was even there."

He also claimed that "China has real economic difficulties" and that China's president "wants to have a relationship [with the US] again."

The comments came just a day after Secretary of State Antony Blinken met with Xi, holding talks that were described as largely positive.

China was predictably less than pleased with Biden's comments, which were termed "ridiculous" by the state's foreign ministry.

"The relevant remarks by the US side are extremely ridiculous and irresponsible, they seriously violate basic facts, diplomatic protocol and China's political dignity," foreign ministry spokesperson Mao Ning said at a Wednesday briefing.

"China is strongly dissatisfied with and firmly opposed to this."

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Russia also chimed in with some criticism. "This is a very contradictory manifestation of US foreign policy, which points to a significant element of unpredictability," Kremlin spokesman Dmitry Peskov told reporters.

Tuesday was not the first time Biden has made significant, even provocative, statements at fund-raising receptions, usually small-scale events at which cameras and recordings are forbidden but where journalists may listen to and transcribe the president's opening remarks.

At one such event last October, for example, Biden spoke of the threat of nuclear "Armageddon" from Russia.