Deby, speaking late on Monday after a two-hour meeting with Central African Republic President Francois Bozize, said: "I do not rule out the Khartoum government repeating another aggression against Chad."
Such an attack was being planned at al-Ginana in western Sudan, "where Sudan has sent a motorised column some 50 vehicles strong", Deby declared.
"We strongly fear that through these actions the CAR (Central African Republic) will also be destabilised," he added.
Deby has called for an extra-ordinary meeting of the Economic and Monetary Group of Central African Countries to address the situation.
Aljazeera reports that the African Union on Saturday said it sent a delegation to Chad and Sudan in an attempt to defuse the tension.
The Organisation of the Islamic Conference (OIC) had on Sunday urged Sudan and Chad to exercise self-restraint to defuse the rapidly escalating tension between the two neighbours.
OIC's Ihsanoglu has urged Chad
and Sudan to defuse tensions
The secretary-general of the world's largest Islamic body, Ekmeleddin Ihsanoglu, said the two countries should "demonstrate self-restraint and calm the situation", after Ndjamena's accusation that Khartoum was trying to destabilise its government.
The AU said on Saturday it had sent a delegation to Chad and Sudan in an attempt to defuse tensions as Chad declared it was in a "state of belligerence" with Sudan.
The mission was sent as already strained ties between the two nations plummeted on Friday with Chad's declaration, after increasingly bitter accusations have been lobbed back and forth by the two capitals.
Ndjamena charges that Khartoum is trying to destabilise Chad by hosting rebels and a growing number of Chadian army deserters in western Sudan, from where an attack was launched on Adre on 18 December 2006.
Several new rebel groups have sprung up recently in eastern Chad, a region ingulfed by about 200,000 refugees from the civil war in Sudan's Darfur region.
Khartoum had accused Ndjamena of deploying planes and troops on its territory before the latest incident.