* Chad has roughly 850 troops in 6,000-strong AU mission
* Decision a blow to French efforts to build strong force
* EU contingent due to deploy at the end of next month (Writes through with details, background)
By John Irish and Madjiasra Nako
PARIS/N'DJAMENA, April 3 (Reuters) - Chad said on Thursday it would withdraw its troops from an African Union peacekeeping mission in Central African Republic, a setback to attempts to build a large international force to stem religious conflict in the impoverished country.
Chadian soldiers have been at the heart of African efforts to stabilise CAR but its forces have been accused of siding with the mainly Muslim Seleka rebels whose seizure of power last year sparked tit-for-tat violence with Christian militia.
"Despite the sacrifices we have made, Chad and Chadians have been targeted in a gratuitous and malicious campaign that blamed them for all the suffering in CAR," Chad's foreign ministry said in a statement announcing the planned withdrawal.
It said its troops would remain in place while the practicalities of the withdrawal were confirmed. There was no official reaction from France or the A.U. force, known as MISCA.
However the decision appeared to be a setback for France, which has deployed 2,000 troops in a bid to restore peace to its former colony, a landlocked nation rich in gold, diamonds and uranium that has seen little but instability since independence in 1960.
The dominant military force in the region, Chad has established itself as a key African ally for Paris and contributed roughly 850 troops to the 6,000-strong African Union peacekeeping mission.
"We have to assess the impact but for sure it won't be simple given Chad was a key player in the MISCA mission," a French diplomatic source said.
EU CONTINGENT EXPECTED NEXT MONTH
Seleka seized power in March 2013 but was forced to step aside in January after failing to stem violence that U.N. experts have warned pushed the country close to genocide.
In the wake of Seleka's withdrawal, Muslims have been targeted by Christian militia, forcing most to flee the country or move to the north, where the rebels pulled back to.
Chadian troops have played a key role in escorting Muslim civilians to safety, but were accused at the weekend by local Red Cross and witnesses of killing at least 10 civilians in the mainly Christian capital Bangui, the latest in a series of incidents.
At its peak, around 1 million people were displaced by the violence. At least 2,000 people have been killed since December alone.
Underscoring the scope of the violence, Human Rights Watch said on Thursday Christian 'anti-balaka' militia killed at least 72 Muslim men and boys - some as young as nine - in two attacks that took place in February but had not been widely reported.
The group said Seleka fighters, aided by Peuhl cattle herders, then killed 19 people on Feb. 22.
Rights groups have called on the United Nations to fast track the deployment of a peacekeeping mission to stop violence.
A long-promised European Union force of 800 troops that will be tasked with securing Bangui's airport and improving security in the capital is due to start deploying to Bangui by the end of next month.
However, officials in Paris have indicated that some of the 800-strong EU contingent will be French troops that are already deployed and will be re-hatted. (Additional reporting by Marine Pennetier in Paris; Writing by David Lewis; Editing by Daniel Flynn and Sonya Hepinstall)