US lawmakers will vote Tuesday on impeaching Joe Biden's immigration chief over the border crisis, a hugely unusual maneuver seen by Democrats as a political provocation ahead of November's presidential election.

The move has been led by hardline Republicans in the House of Representatives who have been targeting Homeland Security Secretary Alejandro Mayorkas for months over a surge in illegal entries across the southern border.

Republicans are sweating on what is expected to be a close vote, and even if Mayorkas is impeached -- the political equivalent of an indictment -- he is certain to be acquitted at his trial in the Democratic-led Senate.

The House -- which has only impeached one other cabinet official, Secretary of War William Belknap in 1876 -- will take one vote on two articles accusing Mayorkas of failure to enforce the law and of lying to Congress.

If all 431 House members are present and voting, Republicans -- who command a narrow majority in the lower chamber -- can afford to lose just three votes and two figures on the right of the party are already rebelling.

"The failure of the Biden administration to rein in an open border is a national disgrace and will be a stain on his presidential legacy," Colorado's Ken Buck wrote in an op-ed for congressional newspaper The Hill.

"However, the truth is that this is a policy disagreement masked as an impeachment."

California's Tom McClintock released a 10-page memo accusing his party of failing to identify an impeachable "high crime or misdemeanor."

"Clearly the founders worried that the power of impeachment could be used to settle political disputes and so searched for limiting language to avoid such abuse," he said.

'Political process'

The vote comes amid a showdown between the House and the Senate over curbing a surge in illegal immigration that led to a record 10,000 apprehensions a day at the border in December.

House Republicans have been accused of acting in bad faith over the Mayorkas impeachment after coming out against a bipartisan Senate deal that would impose the toughest asylum and border policies in decades.

House Democrats will vote in unison against the impeachment, which is also vehemently opposed by the White House and the Department of Homeland Security (DHS).

"Impeachment in these circumstances, and on this record, would represent a radical and dangerous step in violation of the Constitution," Homeland Security lawyers Jonathan Meyer and David O'Neil said in a letter to the House Rules Committee.

"The House of Representatives should reject the proposed Articles of Impeachment."

If the vote goes against Mayorkas, the Senate would be compelled to at least open a trial, although it could vote to dismiss the articles, dissolve the trial or refer the articles to a committee.

"I think it is baseless. I think it's a political process, and I am not engaged in politics," Mayorkas told The New York Times Magazine as part of a charm offensive with the media.

He railed against Republicans' "accusatory, rather than solution-focused" politics in an interview in The Washington Post.

A Senate trial would likely come after the chamber returns from its two-week Presidents' Day recess later this month.

"Our goal is to get 218 Republicans, and I'm confident that we're going pass that," Majority Whip Tom Emmer told NBC News. "The issue is pretty clear: The secretary has willfully refused to do his job securing the southern border."

© Agence France-Presse