Democratic presidential candidate Kamala Harris said on Sunday that “no one can sit on the sidelines” in this year's presidential election, capping a day of campaigning across the largest city in the crucial battleground state of Pennsylvania.

“We are focused on the future and we are focused on the needs of the American people," Harris said, "as opposed to Donald Trump, who spends full time looking in the mirror focused on himself.”

Speaking at a city recreation centre, the US Vice President singled out young voters, praising them for being “rightly impatient for change," and told the audience that “there is too much at stake” in the campaign.

“We must not wake up the day after the election and have any regret about what we could have done in these next nine days," Harris said.

Energising voters in Philadelphia, a traditional Democratic stronghold, is crucial for Harris’ chances of beating Republican presidential candidate Trump.

If turnout falls short here, she will struggle to overcome her opponent's advantages in the state's rural areas.

Meanwhile, Trump hosted a rally featuring crude and racist insults at New York’s Madison Square Garden on Sunday.

With just over a week before Election Day, speakers at the New York rally labelled Puerto Rico a “floating island of garbage” and called Harris “the devil”.

“I don’t know if you guys know this, but there’s literally a floating island of garbage in the middle of the ocean right now. I think it’s called Puerto Rico,” said Tony Hinchcliffe, a stand-up comic whose set also included lewd and racist comments about Latinos, Jews and Black people, all key constituencies in the election just nine days away.

His joke was immediately criticised by Harris’ campaign as it competes with Trump to win over Puerto Rican communities in Pennsylvania and other swing states.

Puerto Rican music superstar Bad Bunny backed Harris shortly after Hinchcliffe's appearance.

The normally pugnacious Trump campaign took the rare step of distancing itself from Hinchcliffe. “

This joke does not reflect the views of President Trump or the campaign," senior adviser Danielle Alvarez said in a statement.

But other speakers also made incendiary comments.

Trump’s childhood friend David Rem referred to Harris as “the Antichrist” and “the devil" while businessman Grant Cardone told the crowd that Harris' handlers "will destroy our country.” (AP)