Las Vegas, Nevada - President Joe Biden resumed political attacks against Donald Trump on Tuesday for the first time since the assassination attempt on his rival, as the Democrat sought to prop up his own faltering re-election bid.

Biden called anew for Americans to lower the temperature of their heated politics and sought a ban on the type of gun used in the shooting at his Republican opponent's political rally.

But as he returned to the campaign trail with a speech to crucial Black voters at the NAACP advocacy group in Las Vegas, Biden did not hold back against Trump, who was injured in the ear.

Biden said Trump's presidency had been "hell for Black Americans."

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Cheers erupted as the 81-year-old lashed out at the Republican for talking about "Black jobs" during their recent debate – the same debate during which Biden gave a stumbling performance that has plunged his candidacy into crisis.

"Folks, I know what a Black job is – it's the vice president of the United States," said Biden, referring to his running mate Kamala Harris, the first Black and female VP.

But he opened his speech by saying he was "grateful" that Trump was safe after the shooting and said he wanted to renew efforts to ban the kind of semi-automatic rifle that shooter Thomas Matthew Crooks used.

"Join me in getting these weapons of war off the streets of America. An AR-15 was used in the shooting of Donald Trump... It's time to outlaw them," Biden said.

Biden's renewed political focus on Trump comes as calls by some Democrats for him to step down after the debate, briefly silenced by the shooting, resumed.

The Democratic National Committee, meanwhile, is pushing ahead with plans to rush through Biden's own nomination ahead of its convention in August, despite calls to postpone the process.