Washington (AFP) - Presumptive Democratic presidential nominee Joe Biden has predicted that US President Donald Trump will try to postpone the country's November election in an attempt to win.

"Mark my words, I think he is gonna try to kick back the election somehow, come up with some rationale why it can't be held," Biden said during an online fundraiser Thursday.

The 77-year-old former vice president said it is "the only way he thinks he can possibly win."

Six months before US voters head to the polls, Trump's mind is already in election mode.

But with a pandemic raging and job losses climbing to 26.4 million on Thursday, Trump's path to victory may be harder than he anticipated.

Biden, highlighting Trump's recent threat to veto emergency funding for the US Post Office, claimed it was an example of the president's intention to "do all he can to make it very hard for people to vote."

While mail-in voting and absentee ballots remain methods many say could help limit voters spreading coronavirus, Trump maintains they create the potential for fraud.

Meanwhile, dozens of US states have postponed their primary races, which will officially determine who will be the presidential nominee.

The 73-year-old Trump has been criticized for turning his daily White House coronavirus briefings into campaign events -- rallying his base and taking swipes at his detractors such as Biden, who is sheltering at home.

"We have a sleepy guy in a basement of a house that the press is giving a free pass to, who doesn't want to do debates because of COVID," Trump said during the Thursday briefing.