South Sudanese President Salva Kiir this week ordered his forces from the Sudanese border. Both sides in Ethiopia agreed to prepare to establish a demilitarized zone along the border.
"We call on the parties to begin implementation of all aspects of these agreements immediately and unconditionally," a statement from British Foreign Secretary William Hague, Norwegian Foreign Minister Espen Barth Eide and U.S. Secretary of State John Kerry read.
Both sides have squabbled over issues such as oil exports and the status of disputed borders.
U.S. Ambassador to the United Nations Susan Rice this week said she was concerned that, while Sudanese leaders have made similar deals in the past, few have been implemented.
South Sudanese military leaders this week said it would border redeployment was under way. Juba called on its counterparts in Sudan to do the same.
South Sudan in 2011 gained independence from Sudan under the terms of a 2005 peace deal that ended civil war. Since then, border clashes, disputes over oil and ethnic conflict have threatened the peace.