Washington DC - Kamala Harris and Donald Trump enter the final weekend of the most tense US presidential campaign of modern times with a flurry of swing-state rallies that will test their stamina and ability to persuade the country's last undecided voters.

Harris, bidding to become the country's first woman president, will use rallies in Georgia, North Carolina, and Michigan to drive home her message that Trump is a threat to US democracy.

Trump – seeking a sensational return to the White House after losing in 2020 and then becoming the first presidential nominee to have been convicted of crimes – promises a radical right-wing makeover of the government and aggressive trade wars to promote his policy of "America first."

In an interview with Fox News Saturday morning, Trump took a swipe at the state of the economy under the Biden-Harris administration, calling the disappointing job numbers released Friday "a gift to me."

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The candidates' frantic schedules will run right into Monday, culminating with late-night rallies in Grand Rapids, Michigan for Trump and Philadelphia, Pennsylvania for Harris.

Election Day is Tuesday, but Americans have been voting early for weeks, with more than 72 million ballots already cast – including a record four million in Georgia, where Democrats seek to pull out all the stops to keep the state in their column.

Opinion polls continue to show a tied race, particularly in the seven battleground states likely to determine the result in the US Electoral College system, leaving the Republican businessman and his 60-year-old Democratic rival fighting hard to peel off even slivers of support from each other's camps.

Harris, currently President Joe Biden's vice president, is doing that by appealing to centrist voters and propelling her base to the polls with a robust ground game and get-out-the-vote effort.

Thousands of women were expected to demonstrate Saturday, under the theme "We Won't Go Back," in cities across the country in support of Harris and abortion rights.

But as she has worked to appeal to women voters across party lines, using issues like abortion and health care, Trump lashed out at a Democratic TV ad depicting wives of his supporters secretly voting for Harris.

"Can you imagine a wife not telling her husband who she's voting for?" he asked on Fox News Saturday morning.

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Harris, who earlier rebuked Trump for saying he would protect women whether they "like it or not," has encouraged voters to "finally turn the page" on the former president.

"He is someone who is increasingly unstable, obsessed with revenge, consumed with grievance – and the man is out for unchecked power," she told supporters at a rally in Little Chute, Wisconsin on Friday.