Donald Trump has vowed to intensify his crackdown on immigration if he returns to the White House and has left the door open to resuming his most controversial policy.

President-elect Javier Milei has arrived in the US for a trip to New York and Washington that will include meetings with the International Monetary Fund and government officials.

More than 2.9 million people travelled through airport security checkpoints on Sunday, making it the busiest day ever for US air travel, the transport authority said.

Spending online on Cyber Monday is set to reach as much as $12.4 billion, an increase of more than 5.4 per cent from last year.