The Trump administration has imposed a new temporary travel rule that will see citizens of some African countries post bonds of up to $15,000 to visit the U.S.

The pilot program, which will come into effect on December 24, seeks to prevent visitors from 15 African countries listed in the new travel rule from overstaying in the U.S., according to the State Department.

“Visa applicants potentially subject to the Pilot Program include aliens who: are applying for visas as temporary visitors for business or pleasure (B-1/B-2); are from countries with high visa overstay rates,” the statement from the State Department said.

The visa bonds targets countries that have overstay rates of 10 percent or higher as reported in the Department of Home Security (DHS) fiscal year 2019 Entry/Exit Overstay Report. According to the DHS report, the worst offenders were typically from Chad (44.94 percent), Djibouti (37.91 percent), and Mauritania (30.49 percent).

They will be required to pay a refundable bond of $5,000, $10,000 or $15,000. “Visa bonds will be posted with U.S. Immigration and Customs Enforcement,” according to the State Department.

It said the pilot program will help them assess the operational feasibility of posting, processing, and discharging visa bonds which will inform any future decision concerning the possible use of visa bonds to address the national security and foreign policy objectives.

The affected countries include Angola, Burundi, Burkina Faso, Chad, Cape Verde, the Democratic Republic of the Congo, Djibouti, Eritrea, the Gambia, Guinea-Bissau, Liberia, Libya, Sudan, Mauritania, Sao Tome, and Principe.

Historically, consular officials have been discouraged from exercising their authority to require bonds, as reflected in the Foreign Affairs, since the mechanics of posting, processing, and discharging a bond are cumbersome.

Trump made a crackdown on illegal migration a key priority of his presidency, and his latest move could affect many.

President-elect Joe Biden, who has pledged to reverse many of Trump’s immigration policies, is yet to comment on whether it would quash the overstay-prevention program.