Washington DC - President Donald Trump on Tuesday renewed his assault on voting rights with an executive order that requires voters to provide proof of citizenship when registering.

Experts swiftly denounced his executive order as an abuse of presidential power that could ultimately prevent millions of Americans from casting ballots, and rights groups already have vowed to challenge it in court.

Trump, now in his second term, has never acknowledged his defeat to Joe Biden in the 2020 presidential election, and he maintains baseless claims of massive election fraud – particularly in absentee voting, a method which he encouraged during the 2024 elections.

"Perhaps some people think I shouldn't be complaining, because we won in a landslide" last November, Trump said as he signed the executive order in the White House.

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"But we've got to straighten out our election. This country is so sick because of the election, the fake elections," he said. "And we're going to straighten it out, one way or the other."

The new rules will require proof of citizenship to be presented when registering to vote in one's state of residence. US states that fail to comply with the directive could see cuts to their federal election funding.

According to the executive order, the attorney general would be empowered to "take all necessary action... against States that violate these provisions by including absentee or mail-in ballots received after Election Day in the final tabulation of votes."

Several states allow absentee ballots to be counted if they arrive after Election Day, provided they are postmarked before the polls close in their state.

For law professor Richard Hasen of the University of California, Los Angeles, this "dangerous" executive order could "potentially disenfranchise millions of voters."

On his Election Law blog, Hasen called Trump's directive "an executive power grab," and notes that federal elections are largely the responsibility of the states, with Congress setting rules for the conduct of elections.

The Brennan Center, a nonprofit public policy institute, denounced the executive order, posting on X that it "would block tens of millions of American citizens from voting. Presidents have no authority to do this."

The ACLU also slammed the order as "an extreme abuse of power" and suggested legal challenges would be filed. "We'll see him in court," it said.