Peace talks in Ethiopia could end heavy fighting between the government and rebels in South Sudan. Formed in 2011, South Sudan is the world's newest state.
And what happens in the region has global economic implications because oil represents 98 percent of South Sudan's budget revenue.
"It would have been difficult for South Sudan to become an independent country without America's influence, even though of course it was the South Sudanese who died in the long wars and fought for their freedom," says the BBC's James Copnall.
Both the U.S. and China in particular are watching the situation closely.
On Tuesday, the U.S. sent Donald Booth, special envoy to the region, to meet with President Kiir. The U.S. has been sending aid to the country, after years of conflict.