President Donald Trump has accused the Biden campaign of politicising the search for a Covid-19 vaccine, and said Democratic vice presidential candidate Kamala Harris “will never be president.”

“I watched Kamala’s whole numbers drop (during the Democratic primaries) from 15 to almost zero and then drop out even before she ran in Iowa because people didn’t like it. And I understand why she will never be president,” Trump told reporters on Monday in a briefing that he opened with an attack on the Indian-origin California senator.

Harris had said she would not trust any vaccine announced by Trump without credible and reliable information. Calling her the “most liberal person in Congress”, Trump demanded that she should “apologise for the reckless anti-vaccine rhetoric”.

He said she is “not a competent person, in my opinion; would destroy this country and would destroy this economy”.

Trump insisted that a vaccine may be ready “even before a very special date”, referring to November 3, the Election Day. “So now they’re saying, ‘Wow, Trump has pulled this off. Okay, let’s disparage the vaccine’,” he said, adding, “That’s so bad for this country.”

The president denied he was himself politicising the vaccine search by talking about a breakthrough as early as October. “No, I’m saying that because we want to save a lot of lives,” he said, adding, “the faster, the better. With somebody else, maybe they would say it politically, but I’m saying it in terms of this is what we need.”

When asked if she would take the vaccine if it was announced before the election, Harris had said in an interview to CNN, “I will say that I would not trust Donald Trump, and it would have to be a credible source of information that talks about the efficacy and the reliability of whatever he’s talking about.”

Trump has repeatedly claimed a vaccine will have been found by the end of the year for Covid-19 that has killed nearly 190,000 Americans and infected more tan 6.4 million, and sent the economy into a tail spin, with millions of people left jobless by shuttered businesses.

Questions have been raised about Trump’s handling of the epidemic — with most Americans rating it poorly in polls — seriously imperiling his re-election bid.