JUBA (Reuters) - The United States has lost trust in South Sudan s government for fueling the country s civil war and it must bring peace or risk losing support from Washington, U.S. Ambassador to the United Nations Nikki Haley told the nation s President Salva Kiir.  Haley was the first senior member of President Donald Trump s administration to visit South Sudan, which spiraled into civil war in 2013, just two years after gaining independence from Sudan. She met one on one with Kiir for some 45 minutes.   I let him know that the United States was at a crossroads and that every decision going forward was going to be based on his actions,  Haley told reporters after the meeting in the capital Juba. The United Nations has warned that the violence in South Sudan, which has forced some 4 million people to flee their homes, was providing  fertile ground  for a genocide. Kiir s government has denied U.N. allegations of ethnic cleansing. Haley had to cut short a visit to a camp for South Sudanese displaced by the violence amid rowdy anti-Kiir protests.   He understood that Americans were disappointed in his leadership in South Sudan, I made that very clear. And he understood that all the aid or help that he hopes will go forward is not a given,  she said.  Haley did not elaborate on what further action Washington could take, but said that Kiir  got what I was trying to say.  On Monday she said Washington was considering how to pressure Kiir into peace, though noted that withdrawing aid may not work. The Trump administration last month imposed sanctions on two senior South Sudanese officials and the former army chief.  We have lost trust in the government and we now need to regain that trust and the only way to regain that trust is through the actions of taking care of all of the people,  Haley told South Sudan s Eye Radio. She demanded that Kiir allow full and consistent humanitarian aid access and bring peace and stability to the country. She said she pushed a timeline for Kiir to act, but declined to elaborate.  Nhial Deng Nihal, a senior adviser to Kiir, said the president told Haley his government and a U.N. peacekeeping mission in South Sudan had established  mechanisms that work jointly to improve and address the humanitarian problems.  He also told reporters that Kiir said government troops  will also be observing a cessation of hostilities in order to create an atmosphere for dialogue.  The civil war was sparked by a feud between Kiir, a Dinka, and his former deputy Riek Machar, a Nuer. It has plunged parts of the world s youngest nation into famine. A fragile peace deal broke down last year and Machar fled the country. He is being held in South Africa to stop him stirring up trouble, sources told Reuters in December.  Haley had to cut short a visit to a camp in Juba, where U.N. peacekeepers are protecting some 30,000 displaced people, after hundreds of rowdy pro-Machar protesters blocked nearby roads, yelling  Salva Kiir is a killer  and  Welcome USA.  Protesters held a large sign that read  South Sudan IDPs (internally displaced people) and refugees love President Trump, the peacemaker and supporter of human rights.   A spokeswoman for the U.N. mission said the protest  started to gain momentum after (Haley) left, IDPs became upset that she was not able to meet with them.  Haley was meeting with a displaced family when she had to leave early due to security concerns.  The previous U.S. administrations of President George W. Bush and President Barack Obama were heavily involved in the birth of South Sudan, which signed a peace accord with Sudan in 2005 and gained independence in 2011. 