Tourists and business travelers from Zambia and Malawi must pay a deposit of up to $15,000 (Sh1.9 million) when seeking a US visa, the State Department has announced, in a move likened to a visa ban for the African nations, which rank among the world’s poorest.

Payment of the visa bond, which aims to rein in visa overstays, “does not guarantee visa issuance,” the notice posted on Tuesday warned, stating that the fee would be reimbursed if certain conditions are met.

“The bond will be canceled and the bond money will be automatically returned in the following circumstances: The visa holder departs from the United States on or before the date to which he or she is authorized to remain in the United States; or the visa holder does not travel to the United States before the expiration of the visa; or the visa holder applies for and is denied admission at the U.S. port of entry.”

The Trump administration has aggressively clamped down on immigration and continues to tighten requirements for securing US visas.

The visa bond follows the planned introduction of a $250 “visa integrity fee” that foreign visitors are required to pay, separate from their visa costs. The fee is also reimbursable if travelers comply with their visa conditions.

The visa bonds target visitors from countries identified as “having high visa overstay rates, where screening and vetting information is deemed deficient, or offering citizenship by investment, if the alien obtained citizenship with no residency requirement,” a separate notice published in the Federal Register stated.