US President Joe Biden is having "mild symptoms" after testing positive for coronavirus during a campaign trip to Las Vegas on Wednesday, according to the White House.

Biden will fly to his vacation home in Delaware, "where he will self-isolate and continue to carry out all of his duties fully during that time," according to spokesperson Karine Jean-Pierre.

Joe Biden tested positive for COVID-19 and is experiencing minor symptoms, according to the White House.

Karine Jean-Pierre, his press secretary, stated that the US president has been vaccinated and boosted. He's tested positive for COVID twice before.

Mr. Biden, 81, was seen earlier on Wednesday visiting supporters in Las Vegas and speaking at an event. He canceled a campaign speech later that night.

The ailment comes as he is under increasing pressure to step down due to his age, following a bad debate performance at the end of June.

Ms. Jean-Pierre stated that the president intends to sequester himself at his home in Delaware while performing "all of his duties fully during that time.".

Kevin O'Connor, the president's doctor, stated that Mr. Biden came with upper respiratory symptoms such as a runny nose and cough and was given his first dose of Paxlovid.

He felt fine during his first event of the day, but later tested positive, Dr. O'Connor said.

Reporters on the Las Vegas trip said they were rushed to the city's airport following the announcement.

Mr. Biden moved slowly and cautiously up the steps to the plane, as the as the video shows. He was not wearing a mask.

The president was forced to cancel a speech at UnidosUS, a Latino civil rights organisation. The organisation's chief executive, Janet Murgura, confirmed the diagnosis to the audience.

"Thank you all so much for your patience and understanding," she told the crowd.

"Regrettably, I was just on the phone with President Biden. And he shared his deep disappointment at not being able to join us this afternoon. The president has been at many events, as we all know, and he just tested positive for COVID."

The illness comes as Mr. Biden faces increased calls for him to withdraw from the face.

Nearly two dozen Democratic politicians have called for him to step aside in recent weeks, including Rep. Adam Schiff of California, who said today he had serious doubts about whether the president could beat former President Donald Trump.

He called on Mr. Biden to "pass the torch.".

Mr. Schiff said that Mr. Biden "has been one of the most consequential presidents in our nation’s history,"  and he could "secure his legacy of leadership" by allowing another Democrat to step forward.