The U.S. is introducing a $15,000 bond requirement for citizens of 12 additional countries when applying for a visa, Reuters reports, citing a State Department spokesperson.

According to him, the new countries will be added to an existing list of 38 nations, bringing the total to 50 countries, predominantly in Africa. The newly added countries are Cambodia, Ethiopia, Georgia, Grenada, Lesotho, Mauritius, Mongolia, Mozambique, Nicaragua, Papua New Guinea, Seychelles, and Tunisia.

The measure applies to B1/B2 visas for business and tourist travel. The new rules take effect on April 2 and are aimed at reducing the number of overstays in the United States.

The bond will be refunded to applicants if they comply with visa conditions and leave the country on time, or if they do not use the visa.

The State Department noted that the program has already proven effective in combating immigration violations.