European Union diplomatic chief Catherine Ashton welcomed Wednesday's United Nations Security Council resolution endorsing a roadmap for the two countries to end hostilities and resolve their outstanding issues within the next three months.
"The fact that Sudan and South Sudan have both welcomed the roadmap and confirmed their commitment to an immediate cessation of hostilities is an important first step in the right direction," she said.
"These statements must now be matched by actions on the ground and by the immediate resumption of negotiations," starting with talks to address the security concerns of both sides, Ashton added.
"They must show their political and practical willingness to pursue the path of peace, not war."
Ashton said the EU attaches particular importance to the immediate deployment of international observers and other personnel on the ground to monitor what is happening and help ensure compliance.
The first in a series of UN-imposed deadlines appeared to pass quietly along the Sudan-South Sudan border Saturday, but an analyst warned of high-level opposition in Khartoum to the UN demands.
South Sudan declared independence last July in line with a peace deal following a 22-year civil war. But border clashes between the two nations began in late March, focusing on disputed territory and oil resources.