Sudan is three months away from a politically sensitive vote on whether to secede or stay united with the north, its foe in decades of civil war that ended in a 2005 peace deal.

News of the request from southern president Salva Kiir came amid growing tensions along the ill-defined border. Both northern and southern leaders have accused each other of building up troops there.

It was likely to anger northern leaders who want to keep Africa’s largest country united and have accused Western governments of covertly backing southern separation.

People from Sudan’s oil-producing south were promised the referendum as the climax to the 2005 Comprehensive Peace Agreement (CPA) that ended the war.

“Salva Kiir asked for U.N peacekeepers to be deployed along the border between the north and the south,” one diplomat told Reuters, on condition of anonymity, saying the request was made at a meeting in the southern capital Juba on Wednesday.

The diplomat said the request would be considered but the envoys made no promises to the southern president.

Another diplomat with the visiting Security Council delegation confirmed the report but said a deployment was not something explicitly called for in the CPA and would therefore require some “adjustments.”

The UN has 10,000 peacekeepers stationed in Sudan, not counting its joint mission with the African Union in Darfur, most of them in the south and three former civil war battle ground areas along the border.

The UN also had a number of officials stationed along the border, monitoring the north-south cease-fire agreed in 2005, UN spokesman Ashraf Eissa said.