US President Donald Trump Photo: AFP

US President Donald Trump reeled Monday on the eve of his first televised debate against challenger Joe Biden after a bolt-from-the-blue report showed he has been avoiding paying almost any federal income tax for years.

The scoop from The New York Times, reporting that Trump paid only $750 in federal income tax in 2016 and 2017, and none at all for 10 of the previous 15 years, was a shot to the jugular of the self-described billionaire.

Trump, who portrays himself as a hard-nosed businessman on a mission to drain the Washington swamp, dismissed the Times story - which the newspaper says is based on examination of his long-secret tax returns.

"The Fake News Media, just like Election time 2016, is bringing up my Taxes & all sorts of other nonsense with illegally obtained information," he tweeted Monday.

Nevertheless, with several new polls on Sunday once again suggesting Biden has the upper hand, the Republican goes into the debate in Cleveland on Tuesday ever more on the defensive.

A Washington Post/ABC News poll put Biden 10 points ahead of Trump nationally, at 53 to 43 percent support among registered voters, while an NBC News-Marist poll gave the Democrat a similar lead of 54 to 44 in key swing state Wisconsin - which Trump had carried in 2016.

Trump's Democratic challenger is homing in on the president's handling of the coronavirus pandemic and his controversial rush to fill the Supreme Court seat left vacant by the late liberal justice Ruth Bader Ginsburg.

However, the tax report threatens the core of Trump's political identity - that vaunted ability to connect with blue collar voters.

Though its impact on voters was still unclear, the Times report hands Biden piles of new ammunition.

And the Democrat's campaign immediately opened fire with an ad comparing typical income tax payments by ordinary Americans, such as $10,216 for nurses, to that reportedly paid by Trump the year he took office: $750.

The Times story raises new doubts about whether Trump is really the man with the Midas touch as he claims, or a hapless spendthrift owing a lot of people money.

He is the first president in years not to make his tax returns public, claiming he can't because he is under audit.

In his trademark brash style, he also once boasted that getting out of taxes "makes me smart."

On Monday, he tweeted: "I paid many millions of dollars in taxes but was entitled, like everyone else, to depreciation & tax credits."

But according to the Times, Trump's tax returns show he managed large-scale tax avoidance partly because his supposedly successful businesses - particularly the golf courses - are such money losers.

AFP