Sudan on Saturday said it was surprised by Chadian accusations it is supporting Chadian army rebels, and urged its western neighbour to form joint border patrols with Sudan to stop tensions escalating further.
Chad on Friday said it was in a "state of belligerence" with Sudan and accused it of supporting Chadian rebels who launched a failed attack on the border town of Adre on Monday. It also complained to the UN Security Council.
"We are very surprised by this," said Sudan's state minister of foreign affairs al-Samani Wasiylah. "All the channels of communications are open between our two countries. We don't know why they are moving out of the bilateral relations to make these ... threatening statements."
Chad's rebel Rally for Democracy and Liberty (RDL) has said it wants to remove President Idriss Deby from power and has warned it will launch further attacks on Chad. Chadian government forces say they have driven RDL forces from Adre into Sudan's troubled Darfur region.
"We will not let anyone use Sudanese soil to launch attacks against a neighbouring country," Samani told Reuters.
He declined to say whether Sudan would allow Chadian armed forces to cross the border into Sudan to attack the rebels, who are believed to have bases in Darfur.
"We have to first take steps to avoid this. We want to have joint border patrols but they are refusing this," he added.
Chad and Sudan carried out joint patrols in the early stages of a revolt by Sudanese rebels in Darfur, who took up arms in early 2003. Tens of thousands have been killed and more than 2 million forced into miserable camps in the Darfur conflict.
Wasiylah said some elements of the Chadian government had supported the Darfur rebels, although it was not government policy.
He said any Chadian army dissident who sought refuge in Sudan and gave up their arms would be treated as a refugee. He added that the Sudanese army had already engaged Chadian dissidents in Darfur who refused to lay down their arms.
"We are in a very difficult position," he said. He added that Darfur rebels had accused the government of violating a shaky cease-fire by attacking the Chadian dissidents last month.
On Saturday Chadian rebels reported troop movements by both armies in the border region. They said Chad had amassed hundreds of troops on its side of the border.