Donald Trump painted an apocalyptic picture of a country "occupied" by hordes of criminal foreigners in a campaign speech Friday as he escalated his efforts to make November's US election about a migrant crime wave that isn't happening.

With the White House race neck-and-neck in the final stretch, the Republican ex-president has been dividing his closing pitch between a protectionist economic message and riling his largely white, working class supporters by demonizing immigrants.

As his Democratic election rival Kamala Harris pledged to work with Republicans to promote united government, Trump delivered as divisive a speech as he has ever given, wildly exaggerating local tensions and misleading his audience about immigration statistics and policy.

"America is known, all throughout the world, as 'Occupied America.' They call it 'occupied.' We're being occupied by a criminal force," Trump thundered, in an 80-minute appearance in Aurora, Colorado focused almost entirely on immigration.

"But to everyone here in Colorado and all across our nation, I make this pledge and vow to you: November 5, 2024 will be Liberation Day in America," he added, flanked by posters of foreign suspected criminals.

While the US government has struggled for years to manage its southern border with Mexico, Trump has super-charged concerns by claiming an "invasion" is underway by migrants he says will rape and murder Americans.

'Racist lies'

Aurora was the scene of a viral video showing armed Latinos rampaging through an apartment block that spurred sweeping, false narratives about the town being terrorized by Latin American migrants.

Smearing Harris as a "criminal," the convicted felon said falsely that Venezuelan gangs in Colorado had been given permission to shoot police, and spoke darkly of an "enemy from within" that he said was a bigger threat than any foreign adversary.

Trump vowed to tackle migrant gangs using the Alien Enemies Act of 1798 -- which allows the federal government to round up and deport foreigners belonging to enemy countries -- as part of a mass deportation drive he christened "Operation Aurora."

Violent crime, which spiked under Trump, has fallen in every year of President Joe Biden's administration. 

Migrants commit fewer crimes proportionately than the native population, though foreign suspects have been named in a few high-profile cases of violent attacks on women and children, infuriating Republicans.

Encounters with illegal immigrants at the southern border are now about where they were in 2020, the last year of Trump's presidency, after peaking at a record 250,000 for the month of December 2023.

Left-leaning lobby group ProgressNow Colorado rejected "Trump's racist lies about Aurora" in a statement calling the rally "a huge strategic blunder" for his campaign.

'Back where they came from'

Harris, campaigning in Scottsdale, Arizona, provided a marked contrast to Trump as she pushed a message of unity, pledging to institute a "bipartisan council of advisors" in addition to having a Republican in her cabinet.

"In the last several years in our country there are some powerful forces that are trying to divide us as Americans, would cheer us on if we point fingers at each other," she said, adding: "We have more in common than what separates us." 

With less than four weeks to the 5 November election, polls show a race too close to call. The latest Wall Street Journal poll Friday gave Harris slim leads in four of the seven swing states, but all the key contests are within the margin of error.

Aurora's police department told AFP it had only isolated reports of activity in the city by the Venezuelan street gang called Tren de Aragua, while the Republican mayor, Mike Coffman, called Trump's claims "grossly exaggerated."

Trump has similarly promoted the fictitious story that Haitian migrants in Springfield, Ohio, are eating residents' pets.

In Aurora, he repeated his threat to deport the community, which is in Ohio legally, saying they "have to go back where they came from."

Trump moved on to Nevada for a second rally in the gambling hub of Reno, where he pushed many of the same misleading, inflammatory immigration claims, although he led with the economy, an issue where his advantage over Harris has been eroded.

Nevada -- where Las Vegas is located -- has a large service industry and Trump touted his "no tax on tips" policy, earning cheers.