A United States senator engaged in an unusual public display of anger and frustration at a session on Thursday focused on the continued fighting in South Sudan.
"I don't know how representatives of South Sudan can show up at these types of meeting without being totally embarrassed by the actions of their government," declared Bob Corker, chairman of the Senate Foreign Relations Committee.
Senator Corker addressed his remarks directly to officials of South Sudan's US embassy who were in attendance at his committee's hearing entitled "South Sudan: A Failure of Leadership."
"I don't know what kind of government you represent," the influential lawmaker told the South Sudanese diplomats.
His rebuke came in response to an acknowledgment by a US Agency for International Development official that South Sudan government forces and rebel troops have attacked humanitarian workers.
A total of 41 aid givers have been killed since the outbreak of civil war two years ago.
Later in the session, Senator Corker suggested that South Sudan President Salva Kiir and rebel chief Riek Machar "would end up in jail soon under any standard court."
And as part of his questioning of US Special Envoy for South Sudan Donald Booth, Senator Corker added in regard to Mr Kiir and Mr Machar: "We're basically negotiating with people we assume will be in jail soon."
In response, Ambassador Booth said such circumstances present "a great conundrum."
But the special envoy avoided direct condemnation of Mr Kiir and Mr Machar, insisting that the repeatedly violated peace agreement signed by the two leaders in August remained the best hope for ending the war in South Sudan.
Other invited speakers at the Senate committee session offered similar affirmations.
"The peace agreement does provide an exit ramp from the one-way road to hell South Sudan is on," said John Prendergast, founding director of the Enough Project, a Washington-based NGO that works to prevent and end atrocities in East and Central Africa.
Special envoy Booth pointed to the anticipated arrival in Juba on Friday of a rebel delegation as a hopeful sign that efforts to establish a transitional government may now move ahead.
Princeton Lyman, Ambassador Booth's predecessor as special envoy to South Sudan, offered a less positive perspective. He told the Senate committee that if the peace agreement falls apart entirely, the US should work with African countries to impose an arms and trade embargo on South Sudan.
"We are not naïve," Ambassador Booth asserted in a prepared statement to the Foreign Relations Committee.
Mr Lyman, who currently serves as a special advisor to President Obama, said divisions within the Intergovernmental Authority on Development have impeded progress towards peace.