By Phil Stewart
WASHINGTON, Aug 5 (Reuters) - South Sudan's President Salva Kiir and U.S. Secretary of State John Kerry both prodded rebels in the African country to engage in sputtering peace efforts on Tuesday after mediators said they failed to show up for the latest round of talks.
At least 10,000 people have been killed since fierce fighting erupted in the capital, Juba, in December pitting Kiir's government forces against supporters of Riek Machar, his former deputy and longtime political rival.
The conflict has reopened deep ethnic tensions between Kiir's Dinka and Machar's Nuer, in a country which only won independence from Sudan in 2011.
Kiir, attending a summit of African leaders in Washington, said Machar did not control forces under his command. He voiced support for a ceasefire but added: "We get difficulty on the side of the rebels."
"I always say that Riek Machar is not in control of what he calls his army. And so each commander in different areas are operating on their own," said Kiir. It was his first visit to the United States since 2011, a State Department official said.
U.S. Secretary of State John Kerry also criticized Machar over breaches in the ceasefire and said the crisis was made all the more urgent by the growing risks of famine in South Sudan.
"(Machar) needs to understand the importance of living by the agreements," Kerry said ahead of talks with Kiir, urging progress on both sides.
As camera shutters clicked, Kerry joked quietly that "it sounds like machine guns."
Hours later, the Inter-Governmental Authority on Development (IGAD), a regional grouping brokering negotiations in Ethiopia, issued a statement saying Machar's side failed to turn up for latest round of talks, which had only begun the previous day. It urged them to return on Wednesday.
Kiir and Machar signed a second ceasefire deal on May 9, and agreed to thrash out details for the formation of a transitional government. Further progress has been marred by disagreements.
Meanwhile, aid agencies say South Sudan could be headed for the worst famine since the mid-1980s, when malnutrition swept through East Africa and killed over a million people.
On Monday, Donald Booth, the U.S. special envoy to South Sudan, estimated that roughly 40 percent of the population is in need of emergency humanitarian assistance. He said there could be famine seen in parts of South Sudan in the next month or so.
"The most important thing, I know President Kiir agrees with this, is to make sure that people are able to find security and hopefully that we're able to get food, medicine, humanitarian assistance to people at a time of huge need," Kerry said. (Additional reporting by Aaron Maasho in ADDIS ABABA, editing by G Crosse)