US presidential candidate Hillary Clinton was suffering from pneumonia since Friday, September 9, her doctor Dr. Lisa Bardack said. The Democratic Party nominee abruptly left a 9/11 ceremony in New York City, with video footage showing Secret Service agents assisting her into a van.

"Secretary Clinton has been experiencing a cough related to allergies. On Friday, during follow-up evaluation of her prolonged cough, she was diagnosed with pneumonia," said Dr. Bardack in a statement, who added that the former State Secretary has been "recovering nicely" and rehydrated.

Clinton's campaign team, however, made it clear that they're set to cancel their two-day campaign leg in California. The ex-New York State Senator was scheduled to speak before campaign fundraisers on a speech about the economy, the BBC reported.

Dr. Bardack advised Clinton to take some time off the campaign to fully recover from pneumonia. "She was put on antibiotics, and advised to rest and modify her schedule," the doctor's statement further elaborated.

Clinton addressed her supporters in a Facebook post, saying that she's "feeling fine and getting better."

Arriving at the 9/11 ceremony in the wake of her comments against Republican Party supporters, Clinton has since apologized on Saturday for calling them "deplorable." She, however, continued to criticize her Republican rival Donald Trump, saying that she'll continue fighting "bigotry and racist rhetoric."

Trump, for his part, took some time off from his fiery stance against Clinton by wishing her well, the Huffington Post reported. He also maintained that he doesn't take pleasure in the Democratic candidate's illness, amid questions on her physical fitness raised by the Republican camp early on in the campaign.

Attesting Clinton was "in excellent health and fit to serve as president of the United States" in a statement last month, Dr. Bardack cited the ex-senator's full recovery from her 2012 blood clot surgery. Such was in response to Trump's accusations that she "lacks the mental and physical stamina" to become President.