An increase in the number of people from Nicaragua and Cuba arriving at the U.S.-Mexico border last month led to the highest number of illegal border crossings in a given month recorded during President Biden’s administration.

The big picture: The surge in migrants came just before Biden unveiled a policy to curb illegal border crossings, telling migrants from Cuba, Nicaragua and Haiti to "not just show up at the border."

By the numbers: More than 216,000 migrants were stopped at the southwest border in December, marking an 11% increase from the previous month, according to U.S. Customs and Border Protection.

• Of those, 36%, or more than 77,000 people, were from Cuba or Nicaragua.
• Another 24%, or nearly 52,800 encounters, were from Mexico and northern Central America. That's a 6% drop from December 2021.

Meanwhile, Venezuelans, who previously constituted a part of the increase, continued to arrive at far lower numbers, CBP said, attributing it to the migration enforcement process that includes expulsions to Mexico.

• The number of Venezuelans unlawfully crossing into the U.S. from Mexico was down 82% last month from September 2022, per the agency.

Zoom out: Biden announced earlier this month that the U.S. would offer legal entry for up to 30,000 migrants and asylum seekers a month from Nicaragua, Haiti and Cuba — in addition to Venezuela.

• Applicants will be allowed to reside in the country and work for two years but must have a U.S. sponsor and go through a vetting process.
• Meanwhile, it also leverages Title 42, a pandemic rule, to rapidly expel up to 30,000 migrants from those four nations to Mexico each month if they attempt to cross the U.S. border illegally rather than going through the parole process.

Zoom in: The same process has been in place for Venezuelans since October, and the number of Venezuelans attempting to cross the border has since declined.

What they're saying: "Early data suggests the expanded measures for Cubans, Haitians, and Nicaraguans are having a similar impact, and we look forward to sharing the additional data in the next update," CBP Acting Commissioner Troy Miller said in a statement.