The UN Secuirity Council has imposed an arms embargo on South Sudan and sanctions on two militarity officials.
Nine countries backed the US-drafted resolution. Russia, China and four other countries abstained.
US Ambassador Nikki Haley told the council that support for the arms embargo will send a message to South Sudan’s leaders that “we are fed up with delays and stalling”.
“These are the weapons that armed groups used to shoot fathers in front of their wives and children, to hold up convoys of food aid, or to assault women and girls,” she added.
South Sudan won independence from Sudan in 2011 and has been beset by a civil war which has killed thousands and displaced more than 4.5 million.
Countless efforts to bring peace have failed.
A recently signed ceasefire deal between President Salva Kiir and his former deputy Riek Machar has already been breached.