Washington (AFP)

Kamala Harris and Donald Trump will make a final push to break their bitter deadlock as they head into the last week of the most dramatic and divisive White House race in modern times.

Despite a series of historic upheavals in a US election like no other, polls show the Democratic vice president and Republican former president remain neck-and-neck in the polls as Election Day on November 5 looms.

Both will pull out all the stops to sway voters, with Harris, 60, giving her closing pitch on Tuesday at the same spot where Trump rallied supporters to protest his election 2020 loss before the deadly January 6, 2021 assault on the US Capitol.

Trump, 78, is also relying on spectacle, and he gave a barnstorming rally at the famed Madison Square Garden arena in his home city of New York on Sunday night to kick off his final effort.

As the race goes down to the wire, the two rivals will hammer the seven battleground states where just a few thousand voters could decide who governs the world's top superpower.

A deeply divided United States will make history either way: by electing its first woman president, or by granting Trump a sensational comeback and putting the oldest ever commander-in-chief into the Oval Office.

'Crucial time in history'

The choice reflects the starkly different visions offered by Harris, the first female, Black and South Asian vice president, and billionaire tycoon Trump.

Harris at first focused on a message of joy and positivity after her shock replacement of President Joe Biden at the top of the ticket in July, but has since switched to a relentless focus on Trump as a "fascist" who threatens democracy.

The Democrat has pointedly chosen the Ellipse on the National Mall in Washington for her rally exactly a week before Election Day as it is where Trump spoke to supporters to deny his 2020 election defeat by Biden, shortly before they stormed the Capitol.

"This is a very crucial time in history," supporter Kimberly Whittaker said at a Harris rally in Kalamazoo in the battleground state of Michigan.

The Republican has doubled down on his extreme rhetoric, with his right-wing base further fueled by Trump surviving two assassination attempts over the summer.

Trump has also ramped up his pledge to "Make America Great Again" with a focus on the economy, which like immigration remains a top concern for voters.

'Very competitive'

At the heart of the race are the seven most hotly contested swing states: Arizona, Georgia, Michigan, Nevada, North Carolina, Wisconsin and -- most crucially -- Pennsylvania.

The tightest US presidential election in decades will hinge on who can win over the few remaining undecided voters -- and who can get their base out to vote.

Polls also predict a historic gender gap between the candidates, as well as deep faultlines on race and age.

In the closing days both campaigns will be spending hundreds of millions of dollars on ads while both are also rolling out star surrogates.

Bruce Springsteen and Barack and Michelle Obama have turned out for Harris while on the stump for Trump is tech tycoon Elon Musk.

But Harris may face a bigger challenge overall.

Her campaign had a "better ground game" and more money but Trump "probably still benefits" from a built-in Republican advantage in the idiosyncratic US Electoral College system, said David Karol, who teaches government and politics at the University of Maryland.

"It's very competitive. There's no reason for anybody to be confident."