"The proposal for a neutral force has raised a lot of skepticism in the Security Council, because people don`t consider that the problem is to seal the border between Rwanda and the DRC but to reach a political agreement," he said.
"Creating this force (from scratch) will take months (and) will be very costly ... if you take it from MONUSCO (the UN mission in DR Congo). It means MONUSCO`s ability to protect civilians will be dramatically reduced," he said.
Araud called on M23 rebels to stop fighting and on "all parties, including external actors, to reach an agreement to put an end to the suffering of the population."
DR Congo refuses to negotiate with the M23 rebels, who have been waging an armed rebellion since April.
African leaders met in Kampala, Uganda on Wednesday to discuss the potential for a neutral force to pacify the situation but made little progress.
Members of M23 -- the March 23 Movement -- are drawn from an earlier rebel movement that was integrated into the army in 2009 after a peace deal that M23 claims Kinshasa failed to respect.
Kinshasa accuses Rwanda of supporting M23, which Kigali denies.