Nigeria’s capital city, Abuja, is missing from the Donald Trump administration’s shortlist of 20 African cities where foreigners seeking to travel to the United States can process visa applications.

The U.S. currently has around 50 embassies and consulates across Africa that process visa applications, but the new move by the State Department will slash that number to 20 amid Mr Trump’s crackdown on immigration.

Secretary of State Marco Rubio approved the directive last week, the Associated Press reported, citing senior U.S. officials and an internal memo.

Although no date has been set to implement the change, it is expected to take effect in June.

However, the visa-processing hub in Lagos, Nigeria’s commercial and most populous city, will remain open.

Also remaining open are the centres in Abidjan, Ivory Coast; Accra, Ghana; Addis Ababa, Ethiopia; Cape Town, South Africa; Dakar, Senegal; Dar es Salaam, Tanzania; Djibouti, Djibouti; Johannesburg, South Africa; and Kampala, Uganda.

Others are Kigali, Rwanda; Kinshasa, Congo; Lome, Togo; Luanda, Angola; Malabo, Equatorial Guinea; Monrovia, Liberia; Nairobi, Kenya; Port Louis, Mauritius; Praia, Cape Verde; and Yaounde, Cameroon.

The move will require applicants from countries not included in the list to travel to designated centres in other African nations to process their visa applications.

Meanwhile, consular services will continue in non-hub countries, including U.S. citizens’ passport renewals, emergency assistance, diplomatic visa applications, and special national-interest cases.

The State Department said the development came as it was “constantly evaluating its overseas operations in order to deploy taxpayer resources in a way that advances America’s priorities as efficiently and effectively as possible”.

It said this “includes a visa process that maintains rigorous standards of security screening and vetting and aligns resources and operational capacity with America’s national interests”.

An official told the AP that U.S. diplomats were informed during a conference call last Friday of the development and a planned reduction in personnel at embassies and consulates worldwide.

Already, Nigeria and other African countries have been affected by U.S. travel and visa restrictions due to insecurity and identity vetting challenges; some visa applicants are required to post bonds of up to $15,000.

Recently, authorities introduced additional travel restrictions due to the Ebola outbreak.

Since returning to the White House last year, Mr Trump has moved to limit immigration into the U.S., citing a high rate of visa overstays and identity fraud, among other issues.