US immigration authorities last year deported the largest number of undocumented immigrants in nearly a decade, surpassing the record of Donald Trump's first term in office.

More than 271,000 immigrants were deported from the US over the last fiscal year, according to a report released by the US Immigration and Customs Enforcement (ICE) agency on Thursday.

The ICE report comes just weeks before President-elect Trump, who plans to make mass deportation a cornerstone of his incoming administration, takes office.

President Joe Biden in 2021 had pledged to pause deportations, but his administration ended up expanding it following a surge in border crossings.

In the newly released report, ICE said the steep climb in deportations last fiscal year was partly the result of a streamlined process.

More deportations flights went to further away destinations, including Africa and Asia, which did not accept US deportations for years, the agency said.

A majority of the deportations in fiscal year 2024 involved migrants apprehended by border officials compared to those ICE arrested in the US interior.

Roughly 82% of the 271,000 immigrants deported that year were arrested by border agents.

President-elect Trump has vowed to launch the "largest deportation operation in history" when he returns to office on 20 January.

These promises, however, are likely to face enormous logistical and financial challenges.

Leading up to his decisive victory over Biden in November, Trump spent much of the time on the campaign trail attacking the White House's border policies.

Trump transition spokeswoman Karoline Leavitt told Reuters that Biden's deportations were insignificant compared to the high levels of illegal immigration during his presidency.

"On day one, President Trump will fix the immigration and national security nightmare that Joe Biden created by launching the largest mass deportation operation of illegal criminals in United States history," she said.

The number of migrant encounters along the US-Mexico border reached a record high in December 2023, but have dropped significantly, particularly in the last few months, and are now at their lowest level since July 2020, according to US Customs and Border Protection (CBP).

It also attributed the rise in deportations to improved diplomatic efforts convincing countries to take back more deportees.

Mexican authorities have also increasingly been clamping down on the flow of migrants headed north to the US border.

In June, President Biden issued an executive order that sharply limited asylum which along with Mexico's help led to a decrease in illegal border crossings.

Since then, the number of individuals released by the US Border Patrol pending immigration court proceedings is down 70%, the agency said.