By Mark Doyle
BBC News, Ndjamena
President Idriss Deby of Chad has condemned neighbouring Sudan for, in his words, exporting its war into Chad.
Cross-border fighting has made life in the arid region intolerable
He spoke during a meeting in Chad's capital, Ndjamena, with members of the UN Security Council who are touring Africa encouraging conflict resolution.
Relations between Sudan and Chad are very poor.
This has been a major factor in the humanitarian crisis in central Africa, where more than two million people have been made homeless.
Speaking in his heavily guarded palace in central Ndjamena, President Deby roundly condemned Sudan.
The threat to the security of his country and the entire central African region was, he said, the work of Khartoum.
Deby survived an attempted coup three months ago
As President Deby spoke to the visiting Security Council diplomats, soldiers and plainclothes agents with automatic weapons stood on guard outside the room.
The show of strength was no surprise. Three months ago, rebels entered Ndjamena and tried to overthrow President Deby, before being forced back by loyal troops.
Mr Deby accuses Sudan of backing these rebels and in fact, according to the United Nations refugee agency, both countries openly support rebel activities against the other.
The violence has got worse in Chad, the UN says, since the constitution was changed, allowing President Deby, who came to power in a military coup 16 years ago, to stand for an unlimited number of terms of office.
The cross-border fighting has made life intolerable across a great swathe of central Africa's arid Saharan landscape.
Over two million people are living in remote refugee camps. Rebels on both sides of the border find plenty of embittered people in these camps and recruit them as fighters.
The Security Council diplomats urged President Deby to use dialogue to resolve his differences with Sudan. The Chadian leader said he wanted peace but adopted a tough line.