US President Joe Biden has signed an executive order that would immediately turn down requests for entry into the country by asylum-seekers crossing the southern border illegally, in the event that officials deem the border is overwhelmed.

The long-awaited measure, which Biden has been contemplating for months, would kick in once the seven-day average for illegal crossings between ports of entry along the US-Mexico border hits 2,500 per day, effectively shutting down the border, Xinhua news agency reported, citing senior administration officials.

Given that the daily encounters are already above the threshold now, the order could take effect right after being signed, empowering border officers to repatriate migrants within “days, if not hours,” the officials told reporters during a press call.

Prior to Tuesday’s order, an illegal immigrant seeking asylum in the US would typically be allowed to temporarily enter the country, where the individual will wait for a court appearance to present a compelling case for the request.

Under the new guidance, the border will reopen to those seeking asylum in the US two weeks after the daily crossings stay at or below 1,500 for seven consecutive days.

Unaccompanied children and victims of human trafficking are exempt from the newly-announced restrictions — a key part of the executive order which Biden boasted as out of humanitarian considerations. Immigration advocates, however, worry that such an exemption would potentially lead to a drastic increase of children who make the dangerous journey to the border on their own.

In remarks at the White House announcing the executive order, Biden on Tuesday said his measure, the product of weeks of negotiations between Democrats and Republicans, was opposed by some GOP members of Congress because the former president and his election rival, Donald Trump, “told them to”.

“He didn’t want to fix the issue” of illegal immigration, Biden said of Trump. “He wanted to use it to attack me,” the president said, lashing out at his political foe by claiming that Trump was engaging in an “extremely cynical political move” that amounted to “a complete disservice” to Americans aspiring their leaders to not weaponize but fix the border.