Washington was South Sudan’s key foreign sponsor as it won its independence from Sudan in 2011, but US officials have become frustrated by its descent into chaos and infighting.
The latest measures target information minister Michael Makuei, who is in particular accused of having “engaged in or been complicit in” attacks on the UN mission in South Sudan.
The feared former head of the army, Paul Malong, is also placed on the sanctions list, updated periodically by the US Treasury.
South Sudan’s President Salva Kiir sacked Malong in May, but before that he was accused of being behind the deadly clashes that erupted in the capital Juba in July last year.
Finally, senior military figure, Malek Reuben, the former head of logistics for the Sudanese Peoples’ Liberation Army, is placed on the list, along with three private firms he controls.
US citizens are barred from doing business with individuals on the sanctions list, and any assets they might hold under in areas under US jurisdiction can be frozen.
Treasury also warned US banks “that certain South Sudanese senior political figures may try to use the US financial system to move or hide proceeds of public corruption.”
US State Department spokeswoman Heather Nauert warned that other measures might follow if South Sudanese leaders do not seriously engage in a peace process.
“Six million people in South Sudan -– half of the population -– face life-threatening hunger while more than four million people have been displaced from their homes, including two million refugees,” she said.
“This is a man-made crisis, and one the Government of South Sudan can stop.”