Remarks at campaign fundraising event come just a day after a fence-building visit to Beijing by top diplomat Antony Blinken.
Speaking at a Democratic Party fundraiser in northern California, Biden said Xi had been angered over an incident in February when a Chinese balloon – which Washington says was used for spying– flew over the United States before it was eventually shot down.
“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.
“That’s a great embarrassment for dictators. When they didn’t know what happened. That wasn’t supposed to be going where it was. It was blown off course.”
The balloon incident exacerbated an already difficult US-China relationship, strained over issues from self-ruled Taiwan to semiconductors and human rights, and prompted Secretary of State Antony Blinken to postpone a planned visit to Beijing.
He eventually travelled there last weekend, holding discussions with Foreign Minister Qin Gang, top foreign affairs official Wang Yi, and on Monday afternoon, Xi himself.
Although there were no major breakthroughs, Blinken and Xi did agree on the need to stabilise the rivalry between Washington and Beijing so it did not veer into conflict and Biden indicated afterwards that he thought relations between the two countries were on the right path.
Xi is serving an unprecedented third term as Chinese president and is China’s most powerful leader since Mao Zedong.
Biden, who is 80, is running for a second term as US president in the 2024 election.