US President Joe Biden has launched a wideranging attack on Republican Donald Trump, warning that his predecessor is a threat to American democracy and drawing a sharp distinction between himself and his likely 2024 election opponent.

To make his most extensive critique of Trump this year, Biden, a Democrat, chose an event to honour the late Republican Senator John McCain of Arizona, a former presidential candidate, fighter pilot and Vietnam prisoner of war who Trump had denounced as “not a war hero”.

“There is something dangerous happening in America,” Biden said on Thursday, detailing Trump threats against US officials.

In a speech at the Tempe Center for the Arts in Arizona, a likely battleground state in 2024, Biden noted Trump had suggested in recent weeks that the chairman of the US Joint Chiefs of Staff deserves to be killed and the Department of Justice should be defunded.

Biden also recalled remarks that Trump reportedly made after he abandoned a plan to visit an American military cemetery outside of Paris in 2018. The Atlantic reported at the time that Trump had called the war dead “suckers” and “losers,” comments Trump denied.

“Is John a sucker?” Biden said of McCain, then posed the same question about his son, Beau Biden, who, like McCain, died of brain cancer, which Biden believes his son contracted from military service near an Iraqi burn pit.

Trump’s official campaign social media account on Thursday posted a Washington Examiner story disputing the Atlantic reporting.

Biden drew a sharp contrast between his own beliefs and Trump’s, who has said he considered himself above the US Constitution, the founding documents that lay out a system of checks and balances.

“I believe very strongly that the defining feature of our democracy is our Constitution,” the president said.

“I believe in free and fair elections and the peaceful transfer of power.”

Asked about Biden’s speech, Trump’s campaign spokesman, Steven Cheung, said, “The radical Left Democrats, now led by Crooked Joe Biden, are the greatest threat to democracy the United States of America has ever faced.”

Biden said he does not think all Republicans ascribe to the MAGA agenda, a reference to Trump’s Make America Great Again slogan. But he said, “There is no question that today’s Republican Party is driven and intimidated by MAGA Republican extremists.”

Biden’s message is likely to be repeated often in a campaign race dominated by the Democratic incumbent and the Republican former president. It comes days before a likely government shutdown, a situation forced by Republicans loyal to Trump in the House of Representatives.

Biden’s pursuit of a second four-year term comes amid concerns about his advanced age – he will turn 81 in November – and economic worries in the US He has stepped up his warnings about the potential threat to democracy posed by Trump as exemplified by the January 6, 2021, attack on the US Capitol.

Trump faces multiple indictments, including for his role in the deadly January 6 attack.

– AAP