President Biden dined at an upscale Italian restaurant on the Upper East Side on Tuesday night while his Democratic successor prepared for her presidential debate.

The 81-year-old commander-in-chief was spotted dining at Campagnola on First Avenue for his granddaughter’s birthday, a day before he is scheduled to mark the 23rd anniversary of the September 11 terrorist attacks in Lower Manhattan.

Biden was greeted by cheering spectators as he stepped out of a limousine shortly before 7 p.m. His granddaughter and Hunter Biden’s daughter Finnegan, who turned 24 on Monday, joined him moments later, and the two hugged before heading into the restaurant.

The president nibbled on chicken parmesan and his group sat in the back of the restaurant, two staffers told The Post.

One of the restaurant employees noted that there was “a hell of a lot of traffic” during Biden’s visit. “There was a lot of security. There was nothing we could do.”

The cashier at a neighboring deli said Biden’s motorcade attracted a large crowd that was “screaming and screaming.”

Before leaving for New York, Biden said he wanted to watch the debate between Vice President Kamala Harris and former President Donald Trump at 9 p.m.

The president said he had previously spoken to Harris and given her advice.

“I’ve spoken to the vice president. She seems calm, composed and collected. I think she’s going to do a great job. And I won’t tell you what advice I gave her.”

Harris will join Biden on Wednesday at three different 9/11-related events in three different states – the first of which will take place at the site of the World Trade Center.

The couple will also attend ceremonies at the Flight 93 Memorial in Pennsylvania and at the Pentagon in Washington, DC.

Biden made his most recent faux pas on Tuesday night when he said he was going to New York City to “do 9/11.”

“I’m going to New York for my granddaughter’s birthday, then we’ll watch the debate and tomorrow I’ll do something about September 11,” he told reporters earlier.

Biden’s unfortunate – and inappropriate – wording while attending ceremonies commemorating the nearly 3,000 people killed in the 2001 attacks was quickly noticed by social media users.

“OWE,” posted RNC Research, an X-account managed by the Republican National Committee.