The 12 families in the lawsuit - referred to as Tesfaye vs Blinken - say the US government is unlawfully withholding their visa-hearing process by refusing to reassign the cases to other embassies away from the ones in Khartoum and Addis Ababa, which have not resumed routine visa processing.

Under the US Immigration and Nationality Act, all winners of the Diversity Visa programme must be scheduled for immigrant visa interviews before the end of the fiscal year, which is 30 September, unless a court intervenes.

One of the lawyers representing the families says they have "a once-in-a-lifetime opportunity to become permanent residents" but the government "keeps de-prioritising" their cases.

"If their visas are not issued by September 30, they lose a golden opportunity and so does the United States," says Curtis Lee Morrison.

Rafael Urena, another lawyer, says the US has "failed to live up to its commitments to the African diaspora. Particularly, to Diversity Visa applicants".

A similar case by Iraqi lottery winners in December saw the interview location of the families changed, and the suit was eventually withdrawn.

The Diversity Visa lottery is responsible for the largest percentage of African and black immigration to the US