This week marks the start of the vital post-Labor Day sprint to the November 5 election, and both Harris and her Republican challenger, former president Donald Trump, are expected to ramp up outreach to voters, especially in battleground states such as Pennsylvania, Michigan and Nevada.
At the weekend, Israel recovered the bodies of six hostages from a tunnel in Gaza where it said they were recently killed by Hamas, sparking sharp criticism of the Biden administration's ceasefire strategy and new pressure on Israeli Prime Minister Benjamin Netanyahu to bring the remaining hostages home.
The US government, including Biden himself, has been trying to broker a ceasefire between Hamas and Israel, which has killed more than 40,000 Palestinians in response to Hamas's October 7 attack that killed 1200, for months.
The issue is weighing on the US election, with pro-Palestinian activists threatening to ramp up protests of Harris on the campaign trail and Republicans blaming Biden and Harris for the hostage deaths.
President Joe Biden is under pressure to secure a deal that releases the remaining hostages in Gaza. (AP PHOTO)
On Monday, Biden and Harris will campaign together in Pittsburgh, Pennsylvania, one of the most important battleground states in this election cycle.
Harris will also travel to Detroit, Michigan and her vice-presidential pick Minnesota Governor Tim Walz will travel to Milwaukee, Wisconsin.
Before they campaign, though, Biden and Harris will meet at the White House with the US hostage deal negotiating team to discuss efforts towards a deal that secures the release of the remaining hostages.
Trump will take part in a Fox News town hall on Wednesday and later this week will address the Fraternal Order of Police at their autumn meeting in Charlotte, North Carolina, and hold a rally in Wisconsin.
A recent Reuters/Ipsos poll found Harris was leading the race against Trump 45 per cent to 41 per cent.
Harris and Walz want to keep up the enthusiasm her entry into the race on July 21 sparked among Democrats, who are donating record amounts of money and volunteering by the tens of thousands.
They have focused on an upbeat, positive message about America's future, cost-cutting plans aimed at the middle class and attracting Republicans turned off by Trump.
Trump and his vice-presidential pick JD Vance have struggled to find a clear line of attack against Harris, painting her both as an unrepentant liberal and as the inheritor of Biden's more centrist policies, while also bashing her intelligence and spreading crude internet memes.
Donald Trump accused Kamala Harris of being "weak and ineffective" over Gaza. (AP PHOTO)
Harris's campaign appears to be outraising Trump's - last week, the Harris campaign told the Federal Election Commission that it raised $US204 million ($A300 million) in July, compared with $US48 million reported to the body by Trump's main fundraising group.
Both sides are bombarding battleground states with TV ads.
Biden, Harris and Trump released statements after the six hostage bodies were found.
Biden said he was "devastated and outraged", adding, "Hamas leaders will pay for these crimes. And we will keep working around the clock for a deal to secure the release of the remaining hostages."
Harris said she and her husband had spoken to the parents of Hersh Goldberg-Polin, one of the hostages whose body was found.
"As they mourn this terrible loss, they are not alone. Our nation mourns with them."
Trump said the "hostage crisis in Israel is only taking place because Comrade Kamala Harris is weak and ineffective, and has no idea what she's doing."
