Chad has accused Sudan of being behind a rebel raid on a border town that reportedly ended in 100 deaths.
The rebels want to oust Mr Deby's government
A Chadian minister said Sudan was "wholly responsible" for an attack allegedly launched from Sudan on the eastern town of Adre.
Hourmadji Moussa Doumgor said the raid was repulsed by the Chadian army.
Several new rebel groups have begun operating in eastern Chad recently, led by mutinous military officers who say President Idriss Deby must step down.
The raid on Adre is the second attack in the area in just three days, the BBC's Stephanie Hancock in Chad reports.
The charges were denied by the governor of the Sudanese region of north Darfur, Osman Yusuf Kibir, who said Sudan had never supported the Chadian rebels.
Mr Doumgor, who is Chad's communications minister, said the rebels launched their attack on a garrison in Adre shortly after 0700 local time (0600 GMT), using 17 vehicles.
The minister said the army launched a counter-attack, and the rebels were driven back, sustaining heavy casualties.
There has been no independent confirmation of the death toll given by government in N'djamena.
Aid workers in the western Sudanese province of Darfur reported hearing the sound of explosions and fighting coming from across the border.
Mr Doumgor said that Chad "holds the Sudanese government wholly responsible for this morning's attack, mounted from its territory".
He added that Chadian "government forces are now using their right of pursuit to ward off any further threat" against the border town.
Chad and Sudan has been recently trading accusations amid growing tension on their joint border.
Chad has accused Sudan of hosting rebels, while Khartoum has blamed N'djamena of deploying planes and troops on its territory.
In 2002, the government of Chad signed a peace agreement with one of the main rebel groups, operating in the east of the country.
The Chadian conflict has claimed several thousand lives since 1998.