* South Sudan says recaptures Bentiu, in Unity state
* World's youngest state risks slide into civil war
* U.S. weighs targeted sanctions against S. Sudan - sources (Adds Ban Ki-moon urges Kiir to free detainees)
By Carl Odera
JUBA, Jan 10 (Reuters) - South Sudan's army said it regained a rebel-held northern town on Friday, giving the government control of a region where oil production ...