Washington -- US President Donald Trump on Thursday suggested an unprecedented delay to the 2020 election -- which polls show him losing -- claiming that attempts to provide safe voting during the pandemic will promote mass fraud.

"Delay the Election until people can properly, securely and safely vote???" Trump, who faces Democrat Joe Biden on November 3, asked in a tweet.

Trump claimed that increased mail-in voting, a way to allow people to vote without risking their health in polling stations, would lead to "the most INACCURATE & FRAUDULENT Election in history. It will be a great embarrassment to the USA."

Trump has no constitutional authority to hold back the election.

However, his mere airing of the idea broke with presidential custom, adding to tension mounting in a country ravaged by the coronavirus and set on edge by bitterly partisan politics.

The tweet came minutes after second quarter data showed a 32.9 percent annualized collapse in the economy compared to the first quarter, and down 9.5 percent compared to the same April-June period last year.

Economic pain and mass unemployment is a big reason why Trump finds himself staring down the barrel of defeat in less than 100 days.

Polls show him losing to Biden heavily, including in several must-win swing states, and being relegated to a rare one-term presidency.

"Trump's threat is nothing more than a desperate attempt to distract from today's devastating economic numbers that make it clear his failed response to the coronavirus has tanked the US economy," the Democratic National Committee said in a statement.

"Trump can tweet all he wants, but the reality is that he can’t delay the election, and come November, voters will hold him accountable."

Trump has no authority

Presidential election dates are mandated by law to take place on the first Tuesday after November 1, which this year is the 3rd.

The United States has never allowed a delay, holding elections even during the Civil War, and only Congress could change the timing. With Democrats ruling the House of Representatives, Trump's idea will not get far.

"I wish he hadn't said that. But it's not going to change -- we're going to have an election in November and it's going to be one people should have confidence in," Republican Senator Marco Rubio, a Trump ally, told US reporters in Congress.

Yet all sides agree this election faces a unique set of challenges, with the pandemic still out of control across swaths of the United States.

The most recent surges have been in Republican-led states like Florida and Texas, a politically difficult shift for Trump who earlier in the pandemic suggested that Democrats were to blame for the spread in their states.

In addition, major sporting events have been canceled or curtailed and there are serious doubts across much of the country over whether schools and universities will reopen in September.

Given the virus' threat, there are widespread doubts over how many people will come out to vote and whether sufficient volunteers can be found to staff the polling stations.

During the presidential primary contests earlier this year, several states delayed voting or opened fewer polling sites.

Little evidence for fraud

Trump himself has previously insisted that he sees no problem in going ahead with the election.

But as the general election date approaches, Trump has bitterly resisted Democratic-led attempts to increase availability of mail-in voting, saying that this will promote fraud and that Americans should line up at the polls as usual.

There is no evidence of meaningful fraud in US elections, including when mail-in ballots, which are common in some states, get used.

Trump's opponents are instead calling for more effort to improve the complicated logistics and they accuse the president of trying to suppress turnout.

Trump, a real estate magnate who came to power with a surprise win over Democrat Hillary Clinton in 2016, has spent much of his first term challenging the norms of the White House and he is the first president to seek reelection after having been impeached.

Democrats have grown increasingly suspicious of Trump's intentions as polls point to his defeat.

In April, Biden accused Trump of trying to "kick back the election somehow, come up with some rationale why it can’t be held."