Earlier, Mark Green, the Republican chairman of the House Committee on Homeland Security, criticised Biden's decision to visit the Texas town of Brownsville, which he describes as "one of the slowest sectors on the Southwest border".

The visit, Green says, "makes it abundantly clear that he cares far more about optics than actually addressing this historic, self-inflicted crisis" - and calls it a "desperate photo-op that fools no one".

Other sectors of the border, such as Tucson, Arizona, see upwards of 2,000 daily migrant "encounters" a day, significantly more than Brownsville.

Yesterday, the White House was also asked about why Biden picked Brownsville, but avoided giving a direct answer. "He wanted to show that it was important for him to go down there to hear from Border Patrol agents, to hear from first responders on what’s going on on the ground," the press secretary said.

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