By Hereward Holland
JUBA, Feb 12 (Reuters) - South Sudan on Tuesday accused Sudan of building up forces along their border, in a sign that efforts to set up a buffer zone between the neighbours and resume the oil exports vital to both economies have made no progress.
The two countries came close to war last April in the worst border clashes since South Sudan seceded in 2011 under a peace agreement that ended one of Africa's longest civil wars.
The African Union brokered a deal in September to defuse hostilities. But the nations have failed set up a demilitarised border zone and resume oil exports from the landlocked South Sudan through Sudanese pipelines, as agreed in Addis Ababa.
Such a buffer zone is a pre-condition for Sudan to allow oil exports to restart. Juba shut down its output of 350,000 barrels a day a year ago in a row with Khartoum over pipeline fees.
"The last two months have seen an unusual build-up of forces along our common border with the Republic of Sudan," South Sudan's deputy defence minister Majak D'Agoot told reporters in the capital Juba on Tuesday, without giving any numbers.
"Our forces are in the state of maximum readiness to repel any attack by Khartoum. We will stay in our current positions, we will keep to the terms of the (September) agreement," D'Agoot said.
Sudan's army spokesman and foreign ministry spokesmen could not be immediately reached for comment.
D'Agoot said South Sudan had alerted other countries in the region, the African Union and the U.N. Security Council about what he called recent border violations by Sudan.
"We are concerned again about this hawkish mindset, about the ruling elites in Khartoum who would want to escalate the situation along the border and possibly provoke a war between the two countries," he said.
On Sunday, Sudan's state news agency SUNA said an infantry brigade had boosted security at the Heglig oilfield on the Sudan side of the disputed border. It was not clear if D'Agoot was referring to these troops.
South Kordofan state governor Ahmed Haroun told SUNA the situation was secure and stable at the oilfield, which South Sudan's army briefly seized in April.
The countries are set to resume talks in Addis Ababa this month but diplomats expect no progress in setting up the border zone.
Two meetings between Sudan's President Omar Hassan al-Bashir and South Sudan's Salva Kiir last month failed to break a deadlock due to the deep mistrust between the nations, a legacy of the long civil war.
As well as getting oil flows restarted, both sides also need to decide on ownership of large strips of the almost 2,000 km (1,200 miles) long border.
South Sudan's army said on Saturday it had killed seven fighters from a militia supported by Sudan which had crossed into Upper Nile state. (Additional reporting by Ulf Laessing in Khartoum; Editing by Pravin Char)