Biden imposes new asylum ban at US-Mexico border

Migrants caught illegally crossing the US-Mexico border could be denied the chance to claim asylum and quickly deported or turned back to Mexico under new restrictions announced by President Joe Biden.

The new measures will have exceptions for unaccompanied children, people who face serious medical or safety threats and victims of trafficking, a senior official said on a call with reporters.

Biden, a Democrat, has toughened his approach to border security as immigration has emerged as a top issue in the run-up to November 5 elections where he will face Republican Donald Trump, who has vowed a wide-ranging crackdown if re-elected.

Biden took office in 2021 vowing to reverse some of Trump's restrictive immigration policies but grappled with record levels of migrants caught crossing illegally, a trend that has strained US border authorities and cities receiving new arrivals.

The new deterrent measures "will significantly increase consequences for those who cross the southern border unlawfully," the official said, requesting anonymity as a condition of the call.

During a White House press conference, Biden said asylum access would remain available to migrants who registered for an appointment using an app known as CBP One or used other legal pathways instead of crossing illegally.

"This action will help us gain control of our border and restore order into the process," Biden said on Tuesday.

"This ban will remain in place until the number of people trying to enter illegally is reduced to a level that our system can effectively manage."

The new asylum restrictions are not permanent, a US official told reporters.

Migrants seeking asylum look for transportation after being processed
US authorities have grappled with record levels of migrants crossing into the country unlawfully. (AP PHOTO)

They are activated when the daily average of border arrests tops 2500 over a week and will be paused when arrests drop below 1500 per day, the official said.

The last time crossings fell to that level was in the early months of the COVID-19 pandemic in July 2020 when global travel was at historic lows.

US border arrests averaged 4300 per day in April, according to the most recent government statistics available.

Key operational questions about how the new measures will be implemented remained unclear, however, including how the administration would quickly deport migrants from far-away and unco-operative countries and how many non-Mexican migrants Mexico would accept under the new enforcement regime.

The new restrictions are expected to trigger legal challenges from immigrant and civil rights groups who have criticised Biden for adopting Trump-like policies and backtracking on US legal obligations to asylum seekers.

In advance of the announcement, Trump's campaign issued a statement criticising Biden for high levels of illegal immigration and said the move to exempt unaccompanied minors would encourage child trafficking.