President Joe Biden and former president Donald Trump are both headed to the US-Mexico border Thursday, as the migrant crisis resulting from record-setting illegal immigration is a top issue in their likely election rematch.

Biden, 81, announced his trip Monday, after Trump, 77, had set his own trip there for today to slam Biden’s policies.

“What I didn’t know was that my good friend apparently is going,” Biden insisted during an NYC visit Monday, while a Trump campaign official told The Post that “Biden chasing us to the border … shows just how big of a problem this is for him.”

Trump “will be delivering remarks at the border” the official said.

Biden made the first known visit of his career to the border in January last year after sustained criticism from Republicans over his handling of the mounting illegal immigration crisis.