By Andrew Heavens
KHARTOUM, Jan 29 (Reuters) - Sudan and Chad accused each other on Thursday of backing new attacks by their respective rebel groups in a marked deterioration of relations between the two oil-producing neighbours.
Sudan accused Chadian forces of entering its western Darfur region to ferry supplies to rebels involved in a surge of fighting there. Chad denied the accusation and said Sudan was supporting mercenaries and "preparing a war" against N'Djamena.
Both countries accused each other of using rebels to launch proxy attacks on their capitals last year. Khartoum and N'Djamena resumed shaky diplomatic relations in November.
But relations are back on a knife edge ahead of an expected decision from the International Criminal Court on whether to issue an arrest warrant against Sudan's President Omar Hassan al-Bashir, who is accused of war crimes in Darfur.
Sudan's state minister of information, Kamal Obeid, released a statement saying Chadian forces had entered Darfur to take supplies to the rebel Justice and Equality Movement (JEM).
Obeid said forces linked to Chad's "Republican Guard" had set out to reach JEM forces stationed outside North Darfur's capital El Fasher, the scene of clashes between Sudan's army and JEM earlier this week, but Chad said it was not true.
Sudan's Obeid said Chadian forces had also tried to supply rebel forces in Muhajiriya, a town in South Darfur that JEM seized earlier this month.
"Chad is not willing to engage in normal and stable relations with Sudan," the statement on Sudan's information ministry website quoted the minister as saying.
It did not say whether the supplies reached the rebels across the long and porous border, which the two countries have planned to jointly monitor to prevent the repeated rebel incursions that have damaged their relations in the past.
"PREPARING A WAR"
Chadian rebels crossed the border and attacked N'Djamena in February last year, retreating after several days of heavy battles. Sudan then accused Chad of backing Darfur rebels that reached Khartoum for the first time in six years of fighting.
Chad denied the new charges on Thursday and accused Khartoum of plotting against the government in N'Djamena. Chadian rebels have recently chosen a new leader and are vowing fresh attacks.
"Chadian troops did not cross the Sudanese border," Moussa Faki Mahamat, Chad's Foreign Minister, said in Addis Aaba.
"This is a diversion for the next Sudanese aggression against Chad," he added. "Sudan is organising mercenaries on its territory by giving them military and logistical support. It is clear that (Sudan) is preparing a war against Chad."
JEM denied it has received support from Chad.
Fighting has escalated in Darfur ahead of an expected decision by the ICC on whether to issue an arrest warrant against Sudan's Bashir on charges of war crimes in Darfur.
Sudan says the case is part of a Western plot to remove him and officials regularly accuse unnamed foreign powers of trying to capitalise on the uncertainty surrounding the case.
The Darfur war complicates relations between Chad and Sudan because many of the rebel forces come from cross-border tribal groups. There are also tribal links between Chadian leaders and prominent figures in JEM.
International experts say Sudan's Darfur conflict has killed 200,000 people and displaced 2.5 million more since mostly non-Arab rebels revolted against the Sudanese government in 2003, accusing it of neglecting the region.
(Additional reporting by Moumine Ngarmbassa in N'Djamena; Editing by David Lewis and Richard Balmforth)