The US said on Saturday it would revoke all visas held by South Sudanese passport holders over South Sudan’s failure to accept the return of its repatriated citizens, at a time when many in Africa fear that country could return to civil war.

US President Donald Trump’s administration has taken aggressive measures to ramp up immigration enforcement, including the repatriation of people deemed to be in the US illegally.

The administration has warned that countries that do not promptly return their citizens may face consequences, such as visa sanctions or tariffs. US Secretary of State Marco Rubio stated that South Sudan did not comply with the concept of timely repatriation of individuals when another country, including the US, wishes to take them. “Effective immediately, the United States Department of State is taking actions to revoke all visas held by South Sudanese passport holders and prevent further issuance to prevent entry into the United States by South Sudanese passport holders,” according to Rubio.

It is time for South Sudan’s transitional administration to “stop taking advantage of the United States,” he stated. The South Sudan embassy in Washington did not immediately respond to a request for comment. African Union mediators came in South Sudan’s capital Juba this week for discussions aimed at preventing a new civil conflict after the country’s First Vice President, Riek Machar, was placed under house arrest last week. South Sudanese President Salva Kiir’s government has accused Machar, a longtime foe who led rebel forces during a 2013-18 war that killed hundreds of thousands, of attempting to incite another insurrection.

Machar’s imprisonment came after weeks of warfare in the northern Upper Nile state between the military and the White Army militia. Machar’s forces were aligned with the White Army during the civil war, but they deny any contemporary links. The 2013-18 war was fought mostly along ethnic lines, with Dinka fighters backing Kiir and Nuer fighters supporting Machar.