JUBA - The US Embassy in the South Sudanese capital Juba has ordered the evacuation of more staff from the country, where more than 1,000 people have been killed in three weeks of fighting between rebels and government troops.

An emergency message to US citizens on the Embassy's website said the move was due to a deteriorating security situation. It said there would be an evacuation flight on Friday arranged by the Department of State.

"We are not suspending our operations. We are just minimising our presence," Ambassador Susan Page said.

Fighting has continued in the world's youngest state even as negotiators from both sides arrived in neighbouring Ethiopia for peace talks that are meant to focus first on ending the hostilities.

The Juba government and rebels have agreed in principle to a ceasefire but neither side has indicated when they might lay down their arms.