UNITED NATIONS  (Reuters) - The level of hatred in Central African Republic between Muslims and Christians has been underestimated and is creating a "nearly impossible" situation for African Union and French forces to combat, France's U.N. envoy said on Wednesday.

Speaking at a U.N. event about early warning signs for mass atrocities, Gerard Araud suggested the United Nations consider turning to psychologists or ethnologists to help understand and combat the deadly resentment because religious leaders' calls for calm were being ignored.

Waves of massacres and reprisals by Muslim and Christian militias have killed hundreds, if not thousands, in Central African Republic since rebels seized power in March 2012, waking the world up to the fact that it might be witnessing the prelude to another Rwanda, where 800,000 were hacked, shot or clubbed to death in 100 days in 1994.

France last year hurriedly deployed roughly 1,600 French troops to help a largely ineffective force of African peacekeepers, but they are too thinly spread to prevent tit-for-tat attacks. Araud suggested the job was proving to be much more difficult than Paris had anticipated.

"In Central African Republic I think we had maybe underestimated the hatred and the resentment between the communities," Araud told the event, which was organized to mark the 20th anniversary of the Rwandan genocide.

"It's nearly an impossible situation for the soldiers, the African and the French soldiers," he said. "We have to think in terms of tactics, what to do, in very practical terms to be effective to prevent people from killing each other when they desperately want to kill each other."

A Muslim rebel coalition, Seleka, seized power in Central African Republic last spring, unleashing a wave of killings and looting that in turn sparked revenge attacks by the "anti-balaka" Christian militia.

"We knew that there was some intersectarian violence, but we didn't forecast such deep ingrained hatred," Araud said. "We maybe need to work with psychologists or ethnologists on how did it appear, and now, how to cool down the situation."

The crisis has sent food prices soaring, leaving many households down to one meal a day and 2.6 million people in need of U.N. humanitarian assistance, the U.N. World Food Program said on Tuesday.

U.N. Secretary-General Ban Ki-moon is expected to submit a report to the Security Council next month with recommendations for a possible U.N. peacekeeping force that would take over from the African troops.

Diplomats say they expect Ban will eventually recommend deploying a U.N. blue-helmet force to Central African Republic with a robust mandate to protect civilians. (Reporting by Michelle Nichols and Louis Charbonnea