US Secretary of State John Kerry has expressed frustration in South Sudanese leaders over the implementation of the peace agreement.

The peace deal was signed in August by the by President Salva Kiir, the leader of the opposition, Dr Riek Machar, and the leader of the former Political Detainees, Pagan Amum.

Among other provisions, the agreement calls for immediate cessation of hostilities by both warring parties.

However, there have been reports of continued fighting in Unity State.

Mr. Kerry says the US is determined to help South Sudan out of the conflict, but this would depend on the seriousness of the its leaders.

He was speaking at the Belfer Center for Science and International Affairs at Harvard University on Tuesday.

“You know, sometimes despite all your best intentions, and all of the time you put into something, if the folks you are dealing with just don’t have it in them, are not prepared to make the right choices, unfortunately, you just have to back off, and put your efforts where it can be put,” he said.

“But we are not in any way whatsoever, you can tell from what I just relayed to you, that we are very much front and center right now, and trying to see if we can get something moving and change this cycle of violence that has consumed the youngest nation.”

Mr. Kerry commended Ethiopia, Uganda, and other countries for their efforts in the South Sudan peace process.