(Updates with view of humanitarian agencies)

By Stephanie Hancock

N'DJAMENA, Nov 30 (Reuters) - Chadian anti-government rebels on Friday declared a "state of war" against French and foreign military forces in an apparent warning to a European Union peacekeeping force that plans to deploy soon in eastern Chad.

French troops and aircraft are stationed in Chad under a bilateral defence accord. The EU force, around half of which will be French, is preparing to deploy near the eastern border with Sudan in coming weeks to protect refugees and aid workers.

French President Nicolas Sarkozy played down the threat by the Chadian rebel group Union of Forces for Democracy and Development (UFDD). He said it would not jeopardise the EU deployment in Chad, which is mandated by the United Nations.

The UFDD said in a statement that it now "considers itself to be in a state of war against the French army, or against any other foreign forces in the national territory".

UFDD fighters have been battling government forces loyal to President Idriss Deby in eastern Chad since the weekend in fierce clashes that have shattered a month-old peace accord between Deby's government and his main rebel foes.

Both sides have said hundreds of combatants have died.

The EU force for Chad, which will also send soldiers to the northeast of the Central African Republic, is intended to try to help contain a widening conflict in Sudan's Darfur region, which has pushed armed raiders and refugees across the border.

It will complement a bigger United Nations/African Union peacekeeping force planned for Darfur, where political and ethnic conflict triggered by a 2003 rebellion has killed at least 200,000 people, U.N. experts say.

COMPLEX SITUATION

Asked at a news conference in southeastern France whether the UFDD threat compromised the EU force's deployment, Sarkozy said: "No. And if you want to make me say that the situation in Chad and Darfur is complex, I confirm that.

"If we decided to send a European force to one side of the border and a mixed force on the other side it is because there are problems, conflicts, difficulties. If there were none, we would not have decided to send soldiers."

France is providing around half of the up to 3,700 EU peacekeepers who are due to start arriving early next year in eastern Chad on a U.N. mission to protect camps housing more than 400,000 Chadian and Sudanese refugees.

Humanitarian agencies working in eastern Chad including the U.N. refugee agency UNHCR said they did not feel directly threatened by the UFDD warning, but that any decline in security would hamper their operations.

The UFDD rebels said French military aircraft had flown reconnaissance flights over their positions for the government during heavy fighting on Thursday between the towns of Guereda and Adre, along the border with Sudan's Darfur region.

"Providing diplomatic, strategic and logistical support to the tyrant Idriss Deby is an act of hostility and will be treated as such," said the UFDD statement, sent to Reuters.

Chadian rebels, which Chad's government says are supported by Sudan, have been fighting a guerrilla war for more than two years against Deby's rule. He himself seized power in 1990 in a revolt that began in the east.

On Thursday, Chad accused Sudan of backing the UFDD rebels to try to block the EU deployment. It said the army had seized Sudanese-supplied arms, munitions and vehicles from the UFDD.

Sudan's government routinely rejects Chadian accusations that it supports the rebels. (Additional reporting by James Mackenzie; Writing by Pascal Fletcher; Editing by Kevin Liffey)

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