Joe Biden and Donald Trump exchanged heated barbs Tuesday, attacking each other's competence and credibility, in a fiery first presidential debate 35 days ahead of the most tense US election in recent memory.

There was no handshake as the two men took the stage and while this was due to Covid-19 restrictions, the absence of the traditional greeting symbolised the bitterness engulfing the country in the final countdown to November 3.

Joe Biden and Donald Trump
The 90-minute debate will finally give Americans a chance to see Trump, 74, and Biden, 77, go head to head. Photo: AFP / JIM WATSON

Just minutes in, the debate turned into an all-out and personal brawl as they raced through issues from a Supreme Court vacancy to the coronavirus pandemic to the US health care system.

"Everything he's saying so far is simply a lie. I'm not here to call out his lies. Everybody knows he's a liar," former vice president Biden said.

Biden -- taking on a feisty, aggressive tone despite Trump's taunts that he had low energy -- then told the US president: "Will you shut up, man?"

First presidential debate in Cleveland
Cleveland is hosting the first of three presidential debates. Photo: AFP / SAUL LOEB

"It's hard to get a word in with this clown," Biden snapped at one point.

Biden, who is leading in polls, sought to tie Trump squarely to the Covid-19 pandemic that has claimed more than 200,000 lives in the United States, more than in any other country.

"How many of you got up this morning and had an empty chair at the kitchen table because someone died of Covid?" Biden said.

US President Donald Trump
US President Donald Trump will go hard -- and likely personal -- on challenger Joe Biden. Photo: AFP / MANDEL NGAN

Mocking the 74-year-old Trump for one of his more notorious statements from the White House podium, Biden said: "Maybe you could inject bleach in your arm and that would take care of it."

Joe Biden
Democratic presidential nominee Joe Biden says he's the real blue collar candidate. Photo: AFP / ROBERTO SCHMIDT

Trump hit back that his bleach remark had been in jest and quickly tried to land punches on Biden.

He attacked both his track record as Barack Obama's vice president and even questioned the 77-year-old's educational record.

"Don't ever use the word smart with me. Don't ever use that word with me. There's nothing smart about you, Joe," Trump said.

US President Donald Trump
US President Donald Trump speaks during the first presidential debate at Case Western Reserve University and Cleveland Clinic in Cleveland. Photo: AFP / SAUL LOEB

Trump at one point charged that the "radical left" has Biden "wrapped around their finger."

He also attacked Biden's insistence on wearing a mask to prevent Covid, a decision in line with medical experts' advice.

"You have to understand, I have a mask right here. I put a mask on when I think I need it," Trump said.

Democratic presidential candidate Joe Biden
Democratic presidential candidate Joe Biden speaks during the Iowa Democratic Party Liberty & Justice Celebration in Des Moines, Iowa. Photo: GETTY IMAGES / Joshua LOTT

"I don't wear a mask like him, every time you see him, he's got a mask."

Before they even appeared for the first of three 90-minute TV showdowns, barbs were flying.

Biden, seeking to eat into Trump's crucial support among blue collar voters, capitalized on bombshell revelations that the billionaire Trump managed to avoid paying almost any federal income taxes for years.

Trump -- who has broken longtime presidential transparency by refusing to publish his tax returns -- reportedly used loopholes to pay just $750 in federal tax during the first year of his presidency. He said at the debate that he has paid "millions" in taxes.

Hours before the Cleveland showdown, Biden published his own tax returns -- and at the debate demanded that Trump do likewise.

Facing the threat of being made a one-term president, Trump has pushed a conspiracy theory suggesting his challenger needs performance enhancing drugs and might wear an earpiece to get answers during the debate.

And his campaign communications director Tim Murtaugh amplified a new slur spread on social media that Biden was suspected of planning to cheat by wearing an earpiece.

But right before the debate, Biden responded humorously, tweeting: "It's debate night, so I've got my earpiece and performance enhancers ready."

Underneath was a photo of standard headphones and a tub of ice cream.

Trump went to Cleveland with what he hopes will be a silver bullet -- his nomination of conservative Judge Amy Coney Barrett to replace the late liberal icon Ruth Bader Ginsburg on the Supreme Court.

If Barrett is quickly confirmed, as the Republican-led Senate expects, Trump will have tilted the highest court firmly to the right for years to come.

"I will tell you very simply -- we won the election, elections have consequences," Trump said.

"The Democrats -- they would not even think about not doing it. The only difference is, they'd try to do it faster."

Biden countered that Americans were already voting and should have a say in the Supreme Court justice, raising liberals' fears that Barrett will vote to overturn the right to abortion.

Copyright AFP. All rights reserved.