Donald Trump said on Tuesday that if he is elected president of the United States again, he will not become a dictator except "on day one," despite warnings from Democrats and some Republicans that America risks becoming an autocracy if he wins the 2024 election.

During a televised town hall event in Iowa, Republican presidential candidate Trump was asked twice to deny that he would use his power to seek vengeance on political opponents if re-elected.

"No. No. Other than day one," Trump said when asked to deny he would become a "dictator" if he wins the November election.

Trump stated that he would use his presidential powers on "day one" to close the southern border with Mexico and expand oil drilling.

Trump, who is running for a second term in the White House against Democratic President Joe Biden, has frequently promised "retribution" on political opponents if he regains power.

Biden, prosecutors who have charged him with dozens of crimes, the Department of Justice, and the federal bureaucracy are among the targets, he said in campaign speeches and television appearances this year.

Trump, the Republican presidential frontrunner, was speaking to a friendly audience at a Fox News event in Davenport, Iowa, where the party's nominating contest begins on January 15.

"Donald Trump has been telling us exactly what he will do if he is re-elected, and tonight he said he will be a dictator on day one," Biden's campaign manager, Julie Chavez Rodriguez, said in a statement after the event. Americans should trust him."

Trump served as President of the United States from 2017 to 2021 and has refused to admit defeat to Biden in the 2020 election.

Since then, Trump has spread false claims that the 2020 election was stolen from him, fueling the deadly insurgency by Trump supporters at the United States Capitol on January 6, 2021. Trump's election lies are also central to his current White House campaign.

Trump's rivals for the nomination, including Florida Governor Ron DeSantis and former U.S. Ambassador to the United Nations Nikki Haley, will participate in a televised debate at the University of Alabama on Wednesday at 7 p.m. CST (0100 GMT).

Trump will skip the event, as he has for the previous three Republican debates.

Biden has repeatedly warned that Trump is a threat to democracy and that a second Trump term could usher in a new and dangerous era of American autocracy.

Former U.S. Representative Liz Cheney, a Republican who has been an outspoken critic of Trump and co-chaired the congressional investigation into the Capitol attack, said in media interviews this week to promote a memoir that a Trump dictatorship is a "very real threat" if he is re-elected.