New York - US Ambassador Nikki Haley said on Wednesday the United States is giving up on South Sudan's president after backing the country's independence in 2011 and investing over $11bn, calling him "an unfit partner" in the pursuit of peace and urging an arms embargo on the conflict-wracked nation.She cited President Salva Kiir for almost immediately violating a December 21 cease-fire that took effect three days later, for blocking aid to millions in need despite a promise of "free and unhindered access," and for last month's promotion of three generals sanctioned by the UN Security Council in 2015 for leading "the slaughter" of civilians.In a hard-hitting speech to the council, Haley called the generals' promotion "a slap in the face" of the council, of nations that supported the Kiir government, and "of basic decency."Attempts to ease the suffering of the South Sudanese people aren't working, she said, "and what's worse, we're failing, not despite the leadership of South Sudan, but because of it.""The time has come to acknowledge the hard reality that the leaders of South Sudan are not just failing their people, they are betraying them," Haley said.Her conclusion that "things are going backwards in South Sudan" was echoed by many council members, frustrated as well at the failure of the world's newest nation to end years of deadly political infighting that has claimed the lives of tens of thousands of people.South Sudan plunged into ethnic violence in December 2013 when forces loyal to Kiir, a Dinka, started battling those loyal to his former vice president, Riek Machar, a Nuer. An August 2015 peace agreement has not stopped the fighting, and clashes in July 2016 between supporters of Kiir and Machar set off further violence and spread to other groups. The latest peace deal, organised by the regional group IGAD, was broken in hours."The government of South Sudan is increasingly proving itself to be an unfit partner for this council and any country seeking peace and security for the people of South Sudan," Haley said.She urged the Security Council to support an arms embargo, saying it would slow the violence and flow of arms and ammunition "and protect innocent lives." She noted the council's December 14 statement that it would "impose costs and consequences" on those undermining the peace process.At the African Union summit later this month, Haley urged the continent's leaders "to consider seriously the accountability measures it pledged for those who refuse to pursue peace" - including violators of the cease-fire. She said the AU should also consider establishing a "Hybrid Court for South Sudan" to bring those obstructing peace to justice.UN peacekeeping chief Jean-Pierre Lacroix noted the January 12 joint statement by UN Secretary-General Antonio Guterres and AU chair Moussa Faki Mahamat after multiple cease-fire violations underscoring their intention to support the imposition of "consequences.""The South Sudanese parties must realise that the international community and the region will not continue to tolerate agreements being signed, only to be violated in total impunity," Lacroix said.He also cited "grave abuses" of human rights in South Sudan, especially against women and children."The gravity of conflict-related sexual violence is deplorable and constitutes an emergency in its own right," Lacroix said.Looking ahead, the regional group IGAD - the Intergovernmental Authority on Development - is resuming its High-Level Revitalisation Forum on Febuary 5 in Addis Ababa that is to focus on governance, transitional security arrangements and a permanent cease-fire.Haley said the parties "must find the political will compromise" at the forum and "if they don't the Security Council should work with the region to find a new path to pursue peace."