Officials had hoped direct peace talks would begin in Ethiopia on Saturday after preliminary discussions Friday.
“You need to stop this senseless war today,” Adhanom told the warring factions.
The slow start to peace talks is a worrying sign for South Sudan, which has seen spiraling ethnic-based violence over the past three weeks.
President Salva Kiir accuses the former vice president, Riek Machar, of attempting a coup. Machar denies the accusation, but forces loyal to him control two state capitals, including Bor, about 120 miles north of the capital, Juba.
A spokesman for Machar, Yohanis Musa Pouk, said peace talks will not be held unless a clear agenda is set first.
U.S. Secretary of State John Kerry welcomed the talks in Ethiopia in a press conference in Israel on Sunday, but said they cannot be a stalling tactic or “gimmick” for either side.
“It is only a first step and there is a lot more to do,” Kerry said. “Both parties need to put the interests of South Sudan above their own.”
The United Nations’ top humanitarian official in South Sudan, Toby Lanzer, said Saturday that people were continuing to seek safe haven at two U.N. bases in Juba, where he said the world body is hosting 30,000 refugees. Some 200,000 people are believed to have been displaced by the three weeks of violence.
The U.N. mission in South Sudan said Saturday that it is reinforcing its presence in the country, including police, military and logistics support. Shortly after the violence broke out Dec. 15, the U.N. Security Council voted to temporarily increase the number of U.N. military personnel in South Sudan from 7,000 to 12,500.
The response to the humanitarian crisis has been complicated by the fact the United Nations, aid agencies and embassies have sent personnel out of the country because of the risk of violence. The U.S. Embassy announced Friday it was evacuating more personnel out of an abundance of caution.
— Associated Press