Arizona's top prosecutor says her office is investigating whether Donald Trump violated state law for suggesting a prominent critic should face gunfire in combat.
Trump has drawn outrage for comments he made about former lawmaker Liz Cheney at a campaign event in the battleground state of Arizona.
His campaign said the former president was criticising Cheney as a warmonger, but critics condemned the remarks as evidence he would target his enemies if he wins Tuesday's election against Democrat Kamala Harris.
"She's a radical war hawk," Trump said of Cheney on Thursday.
"Let's put her with a rifle standing there, with nine barrels shooting at her, okay? Let's see how she feels about it, you know, when the guns are trained on her face."
Speaking to a local TV station, Arizona Attorney General Kris Mayes, a Democrat, said Trump might have violated state laws that prohibit death threats.
"I have already asked my criminal division chief to start looking at that statement, analysing it for whether it qualifies as a death threat under Arizona's laws," Mayes told 12News.
Mayes said it was not yet clear whether Trump's comment amounted to protected free speech or a criminal threat.
"That's the question, whether it did cross the line. It's deeply troubling," Mayes said. "It is the kind of thing that riles people up, and that makes our situation in Arizona and other states more dangerous."
The Trump campaign said his remarks had been misinterpreted.
"President Trump is 100 per cent correct that warmongers like Liz Cheney are very quick to start wars and send other Americans to fight them, rather than go into combat themselves," spokeswoman Karoline Leavitt said in a statement.
Both Harris and Cheney, a former top Republican in the US House of Representatives and the daughter of former vice president Dick Cheney, denounced Trump's comments.
Harris told reporters Trump "is increasingly unstable and unhinged".
"Anyone who wants to be president of the United States who uses that kind of violent rhetoric is clearly disqualified and unqualified to be president," she said in Madison, Wisconsin.
Cheney also slammed Trump's comments in a social media post.
"This is how dictators destroy free nations. They threaten those who speak against them with death. We cannot entrust our country and our freedom to a petty, vindictive, cruel, unstable man who wants to be a tyrant."
During the Arizona event, Trump also criticised others who support US involvement in foreign conflicts.
"They're all war hawks when they're sitting in Washington in a nice building, saying, 'Oh, gee, well, let's send 10,000 troops right into the mouth of the enemy'," he said.
Trump has repeatedly talked about "the enemy from within" on the campaign trail and has vowed to prosecute political rivals, election workers, journalists and protesters, among others.
He has said the military could be used against what he calls "radical left lunatics" if there is unrest on election day.
He also has vowed to pardon supporters who stormed the US Capitol on January 6, 2021, in an attempt to prevent Congress from certifying his defeat in the 2020 election.
While serving in Congress during Trump's 2017-2021 presidency, Cheney pressed him to keep US troops in Syria and restore harsh interrogation techniques for military detainees.
She lost her seat in Congress after helping to lead the investigation into the January 6 attack.
