The British government has called on the warring parties to stop fighting and negotiate a peaceful end to the conflict.
There have been reports of fighting between government and SPLA-IO forces in Upper Nile region, particularly in Malakal and Bentiu.
This has led to more killings and displacements.
The Ambassador in South Sudan, Tom Morris, says the talks will not progress well if fighting continues.
Amb Morris issued the statement after a meeting with the Minister of Justice in Juba, Paulino Wanawilla on Monday.
“I would like to add that the absolute priority is of my point of view of stopping the fighting, peace is the desirable outcome and is essential but stopping the fighting, stopping the guns immediately is the urgency,” he said.
“Without that happening, the discussions will be academic. So, we are at every opportunity making the point that the leaders of the party should understand each other and agree to stop the guns.”
Ambassador Morris said the meeting discussed about the justice system in South Sudan.
He says the system should be in line with international conventions.