The US has issued visa restrictions on Cambodia, Eritrea, Guinea and Sierra Leone as these countries refused to take back deported citizens.
The visa restrictions, effective from Wednesday, affected "certain categories of visa applicants, determined on a country-by-country basis", the Department of Homeland Security said in a statement on Wednesday, Xinhua news agency reported.
"Without an appropriate response from the impacted nations, the scope of these sanctions may be expanded to a wider population," it warned.
As stipulated by the visa restrictions, the US Embassy in Eritrea has stopped issuing B visas for all visitors for business or pleasure, and officials of the other three countries were targeted by the visa sanctions.
"These four countries have not established reliable processes for issuing travel documents to their nationals ordered removed from the US," said the statement.
At least 2,137 Guinean and 831 Sierra Leone nationals, many with serious criminal convictions, have been released into the US, it added.
Another 700 Eritrean nationals and more than 1,900 Cambodian nationals were currently subject to a final order of removal.