Secretary of State Marco Rubio said he took the step because South Sudan's transitional government refused to accept its citizens in a timely manner.

Secretary of State Marco Rubio said Saturday he was revoking the visas of all South Sudanese passport holders because the country's transitional government refused to “timely” accept citizens being deported by the Trump administration.
Mr. Rubio also said in a social media post that he would “limit any further renditions to prevent entry” of South Sudanese, blaming the “failure of the transitional government of South Sudan” to accept the returnees. In a statement released through the State Department, Mr. Rubio said: “We will be prepared to reconsider these actions when South Sudan fully cooperates.”
Mr. Rubio’s actions are similar to those announced by President Trump in late January, when he threatened Colombian officials with the revocation of their visas and duties on the country’s exports because they refused to accept U.S. military flights carrying deported Colombians. In that case, Colombia quickly reversed its decision.
Mr. Rubio’s decision to approve such sweeping measures on visas for travelers and immigrants from South Sudan is another sign that the Trump administration is focused on trying to deport as many foreign nationals from the United States as quickly as possible, measures Mr. Trump promised to take during the campaign.
Some of the potential deportees have filed lawsuits against the Trump administration, and several judges have issued temporary restraining orders as a result.
South Sudan's ambassador to Britain, Nixon Deng, said on Sunday that his government had not yet received official communication from the US government on the matter and would not comment further.