Updated

U.S. Ambassador Nikki Haley is warning South Sudan's government and rival forces that Washington is ready to pursue additional measures if they don't take action to end violence, come to the negotiating table and ease the humanitarian crisis in the conflict-wracked country.

Haley told the U.N. Security Council on Tuesday that "words are no longer sufficient" and it's time for action, especially by President Salva Kiir.

She said the government bears primary responsibility "for the killing, raping and torturing in South Sudan" and for ending the four-year conflict and "saving future generations of South Sudanese."

South Korean envoy Bintou Keita said the security situation in the country is precarious and expressed concern at "the real risk of an escalation in violence with the onset of the dry season."