Washington DC - The impeachment trial of President Joe Biden's immigration chief begins Wednesday in the Senate at the behest of Republican lawmakers although the Democrats, who hold the majority in the upper chamber, are expected to quickly move to dismiss it.

The unprecedented impeachment of Homeland Security Secretary Alejandro Mayorkas over disagreements in immigration policy comes as Republicans seek to make border security a key issue in November's election.

In February, lawmakers passed two articles of impeachment accusing Mayorkas of "willful and systemic refusal" to enforce immigration law and "breach of public trust," making him the first cabinet secretary to be impeached in nearly 150 years.

The impeachment – the political equivalent of an indictment – came amid a showdown between the House and the Senate over curbing a rise in undocumented immigration, which hit a record 10,000 apprehensions a day at the US-Mexico border in December.

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But it wasn't until Tuesday that House impeachment managers made the ceremonial walk to present the articles to the Senate in person, along with the House clerk and sergeant-at-arms.

The trial is due to begin in the Senate at 1:00 PM.

The president, vice president, cabinet ministers, and federal judges can be impeached for treason, bribery, and "other high crimes and misdemeanors."

House Republicans have been accused of acting in bad faith, especially after coming out against a bipartisan deal hammered out in the Senate that would have imposed the toughest asylum and border policies in decades.

Democratic Senate Majority Leader Chuck Schumer has pledged to do everything possible to quickly squelch the impeachment proceedings.

"For the sake of the Senate's integrity, and to protect impeachment for those rare cases we truly need it, senators should dismiss today's charges," Schumer said Wednesday on the Senate floor.

Democrats have a 51-49 advantage over Republicans in the upper chamber. Sixty-seven votes are required to remove Mayorkas from office – which will not happen.

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But Senate Republicans have said they will not make it easy for him, and some are insisting a full trial be held.

The situation is less than ideal for Biden, who is campaigning for a second term against Republican White House hopeful Donald Trump. Most of the lawmakers spearheading the fight against Mayorkas are close to the former president.

At his campaign rallies, Trump often mentions horrific murders committed by migrants, insisting the country is in the throes of a crime wave perpetrated by people entering the country illegally, but crime statistics from major US cities and studies conducted by outside experts do not indicate such a phenomenon.

Mayorkas has repeatedly rejected the allegations against him, calling them "baseless" and decrying what he has called political score-settling.

The Senate swiftly disposed of the two articles of impeachment on Wednesday, rejecting them along party lines on the grounds they were unconstitutional.

The White House welcomed the move, saying the Senate has "rightly voted down this baseless impeachment."

"President Biden and Secretary Mayorkas will continue doing their jobs to keep America safe and pursue actual solutions at the border," spokesman Ian Sams said.

"Congressional Republicans should join them, instead of wasting time on baseless political stunts while killing real bipartisan border security reforms."